Self promos - "Cool. Check out...." or "Hey, can you look at...." If you want people to read your stuff, you got to be respectful about it. Share it in forums, or talk about i with someone and bring it up only when it's appropriate.
These are the most annoying comments to get on youtube. "I like your stuff, check out my YT channel!" I think what makes me the most angry is the complete lack of effort to disguise the disingenuous compliment.
"The art makes the whole thing crap"
"I don't know what the hell is going on"
"The art is shit"
Most common comments on Webtoons. I do actually defend myself when I get these comments, I don't think any of us creators should put up with it, since they get it for FREE. (mostly)
I didn't get many comments yet, but it's erotic stuff so I'm guessing it might be like this for a while. I've got someone who complained about the unfairness of my censorship(female VS male kind of argument), which I thought was misguided since I only play by the rules of the site.
On Reddit, i get much more of snarky though, but, that's Reddit.
Recently I had the displeasure to read "okay now take both of your pants off and sit on his sausage" on a really sad episode where my main characters were hugging after talking about suicide attempts. Seriously, people, how should I respond to that!? 
Of course it was on LINE.
Definitely when someone compares your comic with other comics - . - '' I got this comment once: "I'm sorry but your manga kinda reminds me of Deadman Wonderland and Tokyo Ghoul. I also get Mirai Nikki vibes and also some Ajin feels as well". Oh, so you mean a THRILLER?!?! xD
Also, it's frustrating when they complain when the updates are short (it's on Line of course). This is a comment I got once: "I'll come back in a year when there are pages to read for a few minutes". That comment hit me so hard. Every time I get a similar comment I feel more sad than mad.
If I had the possibilities I would make the episodes longer, but what some readers don't consider is that most webcomic artists give away their work for FREE. Which also means that most of us are busy working a fulltime job so that we have a roof over our head and get food on our table. Some of us have even a family to feed and take care of. Time is money. I can't produce more because there's no time although I'd love to draw all day : ( If you want the episodes to be longer, support the webcomic artist just like you do when you buy a book in the bookstore. If you don't want to support the artist or just can't, then do not complain.
And I'm not even exaggerating. It really got to me at the time. I caught myself wondering if my story was any good - or if my readers were just ignoring pages without any hint of "ship sailing". But yeah struggles of having "fujoshis" reading your content.
I haven't received any hate comments (YET), but I have received some annoyingly cringey comments. Some people get too excited when I introduce a new character, and assume they're a love interest to someone. Even though, I thought I was being pretty clear as to who the main focuses were?
So far there hasn't been any bullying of my characters, or any BAD comments persay, but it's annoying nonetheless. I'm just waiting for the hate to eventually flow in. (As they do on any comic, but a lot so on ANY form of BL, I've noticed.)
God those kinds of people annoy me to no end, I'm not even an author, but I'm sick of seeing tripe like that. Especially when it's on a scene or situation where it shouldn't even apply or factor in. Like you know, when the scene involves conversations between two people about past SUICIDE ATTEMPTS! I really do hope whoever posted that was downvoted heavily, and that sentiment was not shared by a good deal of people. Ughh...
I had a scene were a character killed someone, and realized that it was someone that he not only knew but was very close to.
Character was distressed and horrified.
Had a reader in the comments hypothesizing the next page(s) were/should be 'the character fapping'
Because that's what I want to do after potentially killing the most important person in the world to me. Just whip it out and start pounding it.
Edit: There was also another time, where two characters were going to have sex but stopped because of -character development and emotional plot- With someone in the comments complaining, saying things like stop talking and demanding to 'go back to sex' on several of the pages. (heck even if they did 'go back to sex' it would be implied and then faded out to another scene, because I don't draw sex scenes)
Readers asking you to tell them the resolution to a main conflict in the comic... Like sure, let me just spoil this event for you that's been built up for four chapters...
For me, it's usually the one-word comment. I figure, if you're gonna bother to comment, at least give me something worthwhile to respond to.
There's also those who just want you to draw the worst things ever that are their fetishes >3>' I put "accepting requests" on DA, but as soon as I did I got a bunch of over-the-top fetish stuff requested.
There are some real horror stories on here. I haven't gotten any bad comments on my work yet but I find myself periodically coming back to scan this thread, just to steel myself for if and when the day comes 
I will say that the comments of people complaining about having to pay for premium comics REALLY rub me the wrong way - though not as much as comments that direct other users to read licensed premium comics on illegal aggregate sites. A whole site full to the brim with free content and people still feel the need to act like that? Jeez...
They've been spoiled by all the seemingly-free content that's available online. Now they think that the stuff just materializes in people's servers.
"Are you high?"
No, I just have imagination. Sometimes I draw "trippy" stuff, because I like weird things.
I've been really lucky with the comments I've gotten so far, especially here in Tapastic. Mostly people are incredibly nice and polite!
However the one thing that I've run into several times is people telling my comic reminds them of Firefly. Like I get there are similarities but honestly, I'm not even that familiar with the show. I wouldn't be so bothered if people told me my comic reminded them of something I have actually drawn inspiration from, like Cowboy Bebop. But being told my comic is similar to a show I don't even know that well makes me feel kinda awful because the similarities are not intentional.
