I mean, this is kinda just an internet problem in general, but it's just a prevalent here on Lemmy as anywhere else, so it does count as something annoying Lemmy users doing. And that's just general aggression
It seems like saying anything is a great way to get someone downright furious with you. Again, that happens everywhere, I just wish there was less of it on Lemmy. I think FOSS topics are a great example. Just in this thread alone you can see people already getting just... really worked up on both sides of the FOSS subject.
People get really aggressive about what qualifies as a good meme, ffs. And there also just a general culture online (it's died down recently, I think? It was really bad starting in 2016, imo) of humorous aggression, where reacting in really aggressive ways just as a joke is really common, which leads to misunderstandings and causes people to get actually mad if they aren't in the loop of the joke in the first place.
On a bright note however, I have noticed there's a lot less bigotry being treated as acceptable on here. Transphobic memes and stuff of that nature would show up in random communities on reddit a lot more than should ever be acceptable, and they would occasionally (not always) get more support in the comments than they should. Here on Lemmy it seems folks are a lot more proactive in shutting that stuff down before those types get a foothold here. Hopefully it stays that way.