Does a post actually disappear when you click its "hide post" icon?
It does then comes back after.
You said it works in private mode, so there's something going on with your browser.
I can't reproduce your issue here at all, no matter the browser.
Will try at home
At first. But after you refresh or switch from hot,pop, and etc it reappears
Are you sure it isn't a duplicate? Many users have been reposting each-other, daily.
Try to hide a post and check your hidden posts page (sidebar in your profile) to see if it is actually hidden (showing up there).
I wonder if a new reply per post unhides by default?
(post is archived)