R1:dd5d30e643d9

Adjust action strength of self subscribe/unsubscribe

Summary:
Ref T4968. If you add a comment to revision you aren't currently subscribed to, the email currently chooses "[Changed Subscribers]" as the action title. This is less interesting than "[Commented]", provided the affected subscriber is you (adding other people //is// usually interesting).

In this case, reduce the strength of this action below the strength of "comment".

Test Plan: Made several comments in conjunction with implicit and explicit…