Downvoted perfectly good and reasonable comments. Some are the correct answers because you know a lot about a particular thing in the world.
Downvoted perfectly good and reasonable submissions
Reddit mods shadow banning your submissions/comments
Reddit mods deleting your submissions/comments and/or locking them.
People in general just being asses.
I’m not saying that Lemmy is perfect but it feels like both can have a similar vibe. A lot of Lemmy people were/still are Reddit people and so it makes sense that both have similar vibes.