You know that both cookie and password hashing have changed? You may need to clear your old cookies manually to make way for the new ones. Send a mail to the dev list or hit us on IRC in the #bbpress channel and well work out what’s going on.
We’re acutely aware of how spammers attempt to “fool” Akismet. There are steps being taken now to help improve the processes involved in combatting this. Remember that we are users of Akismet too, so have an interest in keeping it ahead of the game.
The nature of Akismet’s purpose means that back-end code needs to remain closed. If spammers knew how it worked, it would likely make it possible for them to game the system. Of course it is opt-in, so if you don’t like it then you don’t have to use it. Controlling the data that is passed to Akismet is controllable from the client end using plugins that can limit it’s behaviour. These already exist for WordPress, bbPress ones could be easily developed too. If there are hooks missing to make that possible then we’ll add them.