As a mail client user, I want Fecru emails from one review to stack

Fecru emails send out emails in batches, but (unfortunately) fecru tells how many events are in the batch in the email subject. That causes email client to be confused whether these emails are a thread or not. In the effect, I got:

1. 5 emails, that a review got 2 new comments,
2. one email each for adding, 1, 3, 5 and 6 comments.

It's a busy review. People comment a lot. That's even more of a reason to allow my email client to collapse them all as one thread (which it is).

If possible, please attempt at removing the number of added comments/changesets etc. from the subject, while keeping the awesome batching feature.