Ask HN: Hacker News Upvote Bug?

I believe that there is a bug in HN. It's hard for me to isolate this but here's how I reproduce it:

1. Logout

2. Navigate to a story

3. Make note of current point value

4. Upvote a user submission

5. Login to HN

6. Make note of 'after' point value and lack of upvote button

What you should notice is that the point value is the same and that the upvote button is gone.

Navigating away and coming back does not seem to register the bug, either. However, I could be wrong and it be a freak incident where every time I've done this (quite a few times incidentally and a couple of times to test it just now) that the comment was down voted.

Edit: Formatting.