as an avid supporter of the Not to Chan movement I would also like to add that I have never in my life called my brother "brother" or "big brother" it's a weird thing to do, maybe it's normal in Japan, but most places it is super weird. I am not that formal with my brother he's family, that's about as close as you get.
I would only use stuff like that if your comic was set in Japan or the characters were Japanese. If your main character is from Brazil and the story is set in Europe, obviously there is no need for random Japanese suffixes.
Just because you are making Japanese-style comics doesn't mean you have to base everything about your work off of what you see from Japanese creators. In fact, Monty Oum (may he rest in peace) did an excellent job of writing believable, English-speaking characters for his anime RWBY.
(At first I thought this was gonna be about "chan" imageboards oops)
Yeah, I'd also say not to use it, maybe unless your characters are Japanese in a Japanese setting. And even then, I'd say it's really not neccessary (and IF you go for it anyway, you should definitely do a bunch of research on what to use in what situation). You can still be inspired by manga and not use everything from them.
It's like having your comic read right-to left like a manga - I almost expect this for translated manga, but if you're not making the comic for a Japanese audience, in Japanese, there's really no reason to do this.
Honestly, I'm not even a fan of it in comics translated from Japanese, let alone webcomics produced in English. It's unprofessional, it makes your work less accessible, and most people using them are just mimicking the way the words are used in anime and manga rather than coming from a place of understanding the language and culture. I'm not really a fan of people producing English language comics that read from right to left either.
I completely support Not To -Chan.
I'm accustomed to reading it in translated manga and anime, but that doesn't mean that I like it. I once read a professional translator being asked on the subject, and he said that a good translator should be able to convey the meaning of honorifics in the target language using the characteristics of that language. Japanese honorifics are unique to the Japanese language, and reading a translation of a Japanese work to other language keeping honorifics and other terms in Japanese sounds like a bad (and quite lazy) translation to me.
I understand that you're asking about English language webcomics done in manga style, so my reasoning is simple: IMO, if having honorifics in a translation is bad, having them in something originally written in English is ten times worse.
Just out of curiosity, what did you call your siblings? By their names? I see folks in US still calling siblings by "bro" or "sis", and I call fam "mom", "dad", "Auntie" or "Uncle." Maybe it's different since we're Asian, not sure.
I also pose another question: honorifics just don't always come over into English well at all. Even with Korean, I could see it being something like oppa (or maybe even 'kuya' with Tagalog) being translated into big bro, but it doesn't really have the same impact unlike when it's just kept as the original term. What do you do then? Go with the translated version w/o the full impact or keep it the same?
I would use whatever is normal in the language you're translating to. I'm from the UK, and my sister and I would never refer to each other by anything except our first names, unless we were mentioning the other to someone else, in which case it would just be 'my brother/sister...'. As long as it's clear to the reader which is the elder sibling, the hierarchy between them shouldn't be too hard to understand. Any culture-specific nuances of the sibling relationship aren't going to be preserved for the reader by using 'oniichan', and anything that can't be conveyed through a combination of the artistic and translation choices is just going to have to be lost.
I think "bro" and "sis" are nicknames, instead of honorifics. Siblings usually just call each other by name, even if it's from a younger to older. You could possibly still use "brother/sister" formally, I've seen some stories that have done that, but only place I've heard "brother/sister" used as honorifics in real life were in religious places.
But if the setting of the story or the heritage of the characters is of a culture which uses honorifics then you could likely get away with leaving them untranslated. Depends on how quickly the reader can deduce the word means "brother/sister" through context clues. I think, in English, indicating the older sibling through honorifics is really going to emphasize the inequal relationship (regarding age and respect) between two characters, so I'd be aware of that.
Someone probably said this (I am sorry for not reading everything). But I think it is not related to the style you are writing it in, but more the origin of your characters. If they are japanese, or inspired by japanese people/culture, it would be normal for them to use chan/san/kun/etc. Or if they are otakus/weeaboos/anime fans/whatever.
Like, The characters from Hearts of Keol are korean/korean inspired and "use" things like "oppa", "sunbae" to call each other.
When you translate you can use like "sr" "mistress", etc, but somethings are hard to equate, like "noona", that's like "older sister" for boys, very specific. I think it that's what your character would be using in their language, it is cooler to not translate, just use "chan".
But if your character isn't japanese, and/or he isn't polite enough, or don't know how to "behaviour", makes more sense if you use different honorifics, or don't use them at all.
A tip for native portuguese speaker characters: we give gender toto stuff when we speak a different language (?) I am saying it because I just did it xD When I refereed to the character as a "he", is is because in portuguese, the word "character" is male, so we use male pronouns when using the generic word "character".
I think it is REALLY insteresting when you research to make characters speak in the way people from the country he is from speaks. I mean, of course it is hard to check the way of talking from every single language you don't know, but it is interesting to add stuff like that. Like... Brazilians rarely use honorifics, just in workplaces, and not always.
So if it is a brazilian talking in japanese with japanese people, chances they are going to drop the "kun" or "chan" or "whatever" are not low. Portuguese (from Portugal) people use A LOT of bad language... And goes on.
I hate it when people insert unnecessary Japanese words like 'sugoi!' 'kawaii!' into their ENGLISH language comics. It's annoying and very weeaboo-ish, and usually an indicator that this comic isn't something to be taken seriously. You can only choose one language: English or Japanese, not a horrible mix of English with any Japanese words you know. So please... don't do that. >< Honorifics are not as bad, but still very unprofessional and I wouldn't use them personally. They could also alienate readers who are not already familiar with Japanese culture and language. However I have seen them being used, even in professional translations, but I don't think they were necessary. Maybe there could be a few exceptions... like if you were writing a very slice-of-life styled comic set in Japan with a lot of jokes based around honorifics, or if you had a few otaku characters that used honorifics with each other. But 99% of the time I think it's unnecessary. There are also English-language equivalents you can use for many honorifics and it would look more professional.
Well, there are a few exceptions in which you could add honorifics and Japanese terms, if you acknowledge that it's going to look weeaboo-ish, For example, imagine that your characters are, in fact, weeaboos, and like to talk that way because they think it's the coolest way to speak. As long as you have a way of lampshading it (having another character who doesn't speak the same way and points it out could be one) the result would be good.
Having them speak in honorifics for no apparent reason... is just a no-no. Have an example: when an English work where people use really specific expressions or wordplay is translated to other language, they translate these expressions too. No translator would have the characters speaking whatever language it is and then having them, for instance, curse in English.
The subject of Honorifics in Japanese hangs on an entire social structure and where everyone fits into that.
Usually the only time you see honorifics in manga is when there is a deliberate attempt to highlight the relationship between two people.
For a series with its origins in English - I'd almost certainly suggest don't.
So if it is a brazilian talking in japanese with japanese people, chances they are going to drop the "kun" or "chan" or "whatever" are not low.
If a Brazilian was in Japan talking with Japanese people, it would be the same as me, an Australian talking with Japanese people.
We are gaijin - "outside" people. We are the bottom of the stack in society. EVERYONE ELSE is at least -san for us. There are no -chans and no -kuns. Even if the person was 3 years old, they still outrank us.
Mostly they are -san, -sama, -tono or -ue.
Not To -Chan!
If you're not Japanese, don't live in Japan or if your story doesn't take place there then please, don't use it!
I agree 100% with you on this one, not only is it weeaboo-ish but it's also vary annoying and I find it sad that a lot of new creators are trying to be so much like the Japanese mangakas when they add all of that. The suffixes, their sound effects and the right to left direction just drives me up a wall...
If you are polite/used to the honorifics, that's how it should be, but I am saying in case the person isn't, or didn't learn about this enough while having Japanese language classes, we are just not used to using honorific.
I am taking Korean classes and feel very uncomfortable whenever it comes to my mind that Koreans treat people older or younger in very different ways, I would drop and ask them to drop honorific all the time. And I am not the only one. A friend said she got crazy how Asians asked her age right away when she was in Germany. But this is not something I am learning in my classes, but mostly from random YouTube videos.
Actually, I draw my manga from right to left. 
If you have the slightest intentions of translating your manga, I don't think the Japanese readers will be pleased with your left to right format. Anyway, it's not that pretentious... Since basically ALL manga actually is read from right to left (unless a translator decides to flip the manga around for whatever reason) A right to left manga in English is not that uncommon, but a left to right manga in Japanese would be weird. This is probably just a personal thing but Japanese sound effects don't bother me, because it helps me learn Japanese sound effects. xD But if you're trying to look professional it definitely doesn't help, since the only time you'll come across Japanese sound effects in an otherwise English manga is if you're reading a fan scanlation... And I don't think anyone wants their manga to look like a scanlation.
