Following up on the previous post, I've extended how I think that this third party notification system should operate. Euan comments on the edge of blogosphere, hopefully a mechanism such as this will blur the edge a bit.
I think that the correct mechanism would be to have each post within MT optionally have a series of email addresses associated with it which form a notification list for incoming comments and trackbacks.
eg I write an article about X, based on thoughts by my friend Igor. When someone writes a comment on the article or send a trackback ping, then Igor gets the same email notification that I do.
I think that this would be a great feature for a new Movable Type release and also with TypePad, as not everyone will want to have a weblog. This mechanism gives non-webloggers an ability to at least participate in the conversation, though it does not offer a clickable hyperlinked name. Thus there is no way for the non-weblogger to gain in reputation, except as a comment author on another's weblog.
UPDATE: Of course it is possible to add this to the normal commenting system. So that people could opt into being notified about further responses to a topic that they have already commented on. A sort of "notify me of further comments" checkbox.
