implement flame-retardant option

[Carnë Draug]

This is more of a feature request than a bug. I have added it to my todo list but it's been there long enough to know that I probably will never get around to do it. I'm posting it here as an idea in case anyone also finds it good and wishes to pick it up.

I had read about the idea the first time on this post (http://www.shirky.com/writings/group_user.html) which does mention mailman. It's a bit long post but near the end, on the "Novel Operations on Social Facts" section proposes some ideas for mailing lists.

There's other worthy ideas there but the one I was planning to implement was the flame retardant in which basically if a user has been too active, its e-mails would be sent with a delay. I think that's pretty neat. Recently the mailing list where I am now is facing such problems. This could be set to the whole mailing list or as an alternative to place an user under moderation (for those that are actual helpful members of the mailing list but have a tendency to get too much involved in flame wars).