Commenting seems to be broken, but in actuality that is not the case.
After leaving a comment a page pops up asking “Are you sure you want to do this?”.
No further action need be taken on your part; the comment has been left.
I’m searching for a solution, but so far no joy. Comment at will, I assure you they stick.
UPDATE: As of 4.29.12 @ 12:30, comments are working as they should. Yay!