Draw by repetition isn't automatic -- one of the two sides has to claim it so that's probably why it didn't occur immediately.
Can't post comments after draw by repetition

Draw by repetition isn't automatic -- one of the two sides has to claim it so that's probably why it didn't occur immediately.
Agree with that, but you should still be able to post comments. I checked, you definitely can after draw by agreement.

White had the right to claim the draw after our move, but never got the chance. It just showed up as a draw by repetition automatically.

They were even more shocked than we were. They were trying to go for a new record of most moves in a vote chess game, but the automatic draw cut them off. On the second last move, there were some votes on the white side to offer a draw, but they didn't reach fifty per cent, and then black's last move shows up in the game log, even though this is the move after the third repetition. There is no record of them voting to claim a draw, and some of their members seemed a bit upset by the turn of events.

Hmm, perhaps I'm mistaken about the application of that rule in Vote Chess, although I'd be really surprised to hear that it's not consistent with the rest of the site.
In vote chess, after a game is automatically declared drawn by repetition, one can no longer post Team Comments.
http://www.chess.com/votechess/game.html?id=15171
Also, the draw was declared a half move after the third repetition rather than immediately.