The Crowd2 plugin is registering users in Jenkins with Full Name = "First Last (username)" instead of just "First Last" or "Display Name" from Crowd.

Crowd2 is also registering the Jenkins user E-mail address = "username" instead of the actual email address listed in Crowd.

These two combine to mean that no commits from Bitbucket are associated with the actual Jenkins user, causing the culprits email to never send.  Editing every single user in Jenkins to correct the email address and full name is required to have commits map to actual users instead of having additional "users" created as committers.