I'd.... be really curious to hear Tapastic's actual stance on profanity, honestly.
Re: swears in comics in general, I don't think this has an overall answer. I think it's specific to the comic. Swearing wouldn't add much to Oops, for example -- not just because "it's an all ages comic" but like, seriously, what would be gained? It wouldn't make any character sound more realistic -- in fact, it would make them sound weird and unnatural, because that character wouldn't fit in the world anymore. Whereas, in a comic like Homestuck, a story about internet relationships between teens told almost entirely through chatlogs, the casual profanity helps ground those characters in reality despite their goofy story, and helps them ring true as teens on the internet.
I think you gotta look at what you're gaining from it -- even if that's something as simple as mood -- and whether that's worth cutting out a potential reader that's uncomfortable with language. I was thinking about this pretty recently for my video game story -- which was more important to me for that story, the accessibility of the story, or making the characters sound like real gamers? The latter isn't important for that story, so I chose the former, but I think either could be a valid answer depending on your priorities. Meanwhile, for Runewriters, I actually have a list somewhere where I decided which swears felt right for the world and which swears felt too strong for the story and sounded out-of-place.
The one thing you CAN'T do effectively is try to please everyone, imo --- if your bad guy calls someone a cowardly @#$%!! that's non-offensive swearing because it's cartoony. If your bad guy calls someone a spineless coward, that's strong and not unnatural without being profane. If your bad guy calls someone a cowardly fuck, it's strong, realistic language, but definitely profanity. All of those options have pros and cons. But if your bad guy calls someone a cowardly f***, you've got the worst of both worlds. It's obvious what the word is, which will be a turn-off for those who don't like profanity, but it instantly makes the language unnatural by calling attention to it in that way. There's nothing gained.