I'm positive that an *apparent* upvote on a comment of mine it's not there anymore: after having left the comment, I was still in the page to read one of the answers a second time when I saw it got upvoted.
A few minutes later the question was at the top of the active questions and I visited it again: no upvote on the comment now, as you can see, but I've noticed that the top answer has been upvoted once more in the meantime (from 2 to 3 upvotes).
I'm positive that the comment appeared as upvoted before I left the page the first time.
I also reloaded the page multiple times, the upvote is still not there anymore.
My speculation is there's something wrong with the JavaScript / AJAX code in the page.