The subject for https://secure.phabricator.com/mail/detail/63209/ (as was received) was
[Differential] [Changed Subscribers] D14076: Allow upgrading in branch `stable`
but "Changed Subscribers" might be the least-interesting part of the content; "Added [inline] Comment" should win this one.
The feed entry has the same information as the subject: https://secure.phabricator.com/feed/6191857304422984251/ (I don't see an entry for "added inline comment" in the feed.