What sort of post or comment gets you downvoted the most? Especially if you don’t think it’s bad behavior in the first place, or don’t care. Does not have to be on Lemmy, but we are here…
One of the good things about Lemmy IMO is that it’s small enough to see the posts that are unpopular. If you do “Top Day” on most channels, you cash reach the bottom, see what people here don’t like.
As far as comments, attempting to rebut the person who is telling me my post sucks, is what gets me into negative numbers most often. The OP is going to voite it down, of course, and nobody else cares, usually.
If you make a comment like that on the wrong instance, that happens, but it’s not like that on every instance. Commie instances are filled with tankies and they have always been very dogmatic, just exhibiting nuance and historical awareness will get you those massive downvotes. Also deeper comment chains on more neutral instances can be weird, but that’s probably small sample bias because few people will dig down that deep.