So, coming from the world of RIF where downvotes haven't been a thing for quite some time:
what are downvotes for in Lemmy?
What am I expressing when I downvote?
I don't agree with the post? I don't want the post to gain notoriety? I don't like the sentiment or the way it's expressed (even if it's factually true)?
Downvotes weren't a thing in Reddit is Fun? I definitely remember downvoting things using RIF right until the end.
To me, I will downvote things that do not deserve any visibility. Such as things that are factually wrong, things that don't contribute, overplayed jokes, hateful posts,...
In addition to what the other user said: some subs were hiding the downvote buttons through their custom subreddit styles. You'd only see this if you used old.reddit though and if you disabled the css (or used an app like RiF) you could downvote as normal.