Voting on a post does mark it as read after you refresh.
I made a post a while ago wishing it was the opposite, haha. On Reddit I would upvote newer text posts with few comments that I think have good potential for discussion, then when I scrolled past them on my feed again I'd take a look. I tried that here but all the posts were getting marked as read so they didn't stand out.
Maybe it depends on what view mode you're in? After seeing your response, I refreshed my home page, up voted the first unread posts, refreshed again and they're all marked read. I'm using the small cards with the buttons underneath the title.