In a production site, I have akismet disabled. Notifications on that one didn’t work. So I thought it could be related to akisment so in another separate site, I have akismet enabled. That didn’t work either.
However, the common thing on both setup is that it was first a release candidate and then I’ve upgraded it to v2.0
In the test setup, I had these plugins installed
akismet
bbpress,
sharecount for facebook
SI Captch Anti spam
tweetmeme retweed button
wp-spamfree
I’m having the same experience now. I’m not getting any reply notifications in bbpress.