Today, I've created an account on askubuntu, and I got the "important notice" bar at the top of the screen, urging me to vote in the Ubuntu&Unix merge/no-merge poll. After clicking through, I was greeted by "This poll closed Aug 29 at 10:43". In my TZ, it is currently Oct 30; shouldn't the notification be disabled?
Your account is two months old, as anyone can see:
<td>member for</td> <td><span class="cool" title="2010-08-16 08:42:04Z">2 months</span></td>
So it seems you had the message inserted a long time ago, and just never visited until then.
(although it is true, we should remove the old messages after the poll ends, but this was really a special case in every way)
Clearly this shouldn't have shown.
I've sent an email to the team pointing them at this thread so hopefully they'll fix it if they haven't already.
Did you visit the site (as a non member) before the end of August? I'm just wondering if it's possible that you had a cookie stored with the message in it and it just displayed once you registered. Seems unlikely but possible.