When I hide posts in my feed I was expecting to not see them again (as it worked in RIF), but I do see them again if I refresh my feed.
I was a RIF user in Reddit, never used Sync before, so maybe this is working as intended. I hope it is a bug as for me hiding posts should prevent the post to appear again in my feed.
Use the lemmy setting to not show read posts, I think it’s a bug that hidden posts come back.