Huh. I've never had a post show up twice. What I am seeing is very specifically posts turning up in the middle of things where they were not before, past the point where I'd think "Oh, they just took a few minutes to hit post." (So presumably those posts got skipped before?)

It's been going on longer than the webservers issue -- I can't pin it down to a date or anything, but I'd taken it as a normal thing while back-reading, as new posts were added to the most recent page. It definitely didn't suddenly start recently.