I receive an e-mail from Phabricator.
The e-mail is about the issue T98498.
It tells me that a person has written a comment, and that a person is now subscribed to the issue.
The comment is interesting, but I don't care about the subscribing.
The subject of the e-mail contains [Changed Subscribers], but not [Commented]. The e-mail hides the (interesting) comment under the (uninteresting) subscribing. I could very well have trashed the e-mail without knowing about the comment.
In this case, please include [Commented] in the subject of the e-mail.