I like this idea a lot, but I wouldn’t want it to be an either/or setting. It’d be perfect if I could set my swipe gesture to hide on upvote, and the upvote button to just mark as read on upvote. Or even just a different swipe gesture for each, would be awesome. Usually I want a post to go away immediately, so I do a lot of vote and hide swipe gestures one after the other. But sometimes I’m weird and want to leave a post in my feed in case I want to go back to it.

For me, if I read a post in a browser instead of the app, and then switch to the app those posts are marked as read, so greyed out a little, but aren’t hidden in the app. I’ve noticed it a lot, and it’s kind of annoying, but it may not be exactly what you’re describing. Pretty sure they persist as read but unhidden in the app even on refresh, which maybe is a bug? Hard to say.