YSK there is a setting in your Lemmy profile to hide posts that you've seen. Upvoting counts as interacting with that post and will hide it after refresh.
Also, if this selected, it will hide any posts you make. I have been saving the posts I make as a favorite until Lemmy fixes this.
I hope we come to a better solution than upvoting things to mark them read and make them go away. That generates a lot of noise in the voting data. Say what you want about whether votes are useful for sorting content, but flooding them with garbage data can only make them worse.
Well you can just click on the post too. The upvote would be like, you've seen a meme, you don't care to click into the post but you like it and don't need to see it again.
Yeah, if there was a "confirm seen" button between up and down voting that'd be good for this. You don't want to register positive or negative for it, just mark it as read. Maybe this should be (optionally maybe) automatic for any post scrolled past?