Normal users can post close votes, but my binding vote won't work. Confirmed by several members in the Teacher's Lounge.
I've backed out the offending changesets and will be building shortly.
The responsible party will be chastened.
Yeah, as I suspected, this appears to be linked to the duplicate dialog bug. You can work around it using developer tools for the moment, by running the following snippet before clicking the close link:
This will unbind one of the duplicate event handlers so that you'll only get a single dialog, and everything appears to work okay from there on out.