zabatonni

Automatically finds duplicate terms (with same name) in each taxonomy, then moves posts from duplicates to its original terms and deletes duplicate terms.
You can choose which duplicates you want to merge and delete.

Merge duplicate terms

Plugin for easy merging duplicate terms (tags, categories, ...)

Jennifer M. Dodd

bbPress Email Notifications provides users with various email notifications relating to forum changes, as well 
as the ability to turn these notifications off. It overrides the bbPress-provided ‘Subscribe’ function, 
allowing users to turn all subscribed topic notifications off and on in one location.
BuddyPress users can update their bbPress email preferences at Member > Settings > Notifications. WordPress 
users can update their preferences at Users > Your Profile.
This plugin deals solely with bbPress plugin forums, and not with BuddyPress group forums.
Filters are available for modification of plugin behavior.
<h3>Credits</h3>
Development funded, in part, by Ariel Meadow Stallings and the Offbeat Empire.

bbPress Email Notifications

Provide notification emails and controls for bbPress subscriptions, merge, and split functions.

Merge duplicate terms vs bbPress Email Notifications