How would you design email notifications for a threaded comments system?

The current system features plaintext comments on pieces of content stored in a mySQL database, and I'm looking to add email notifications.

Current ideas:

• Emails to each user in the thread (no matter how deep)?
• Email only to the owner of the comment you are replying to?
• Email to content ow开发者_JAVA技巧ner for each new comment? Only root level comments?
• Email only to users that check off a 'Notify me of replies' below each content piece, containing any new comment, threaded or not

Thoughts?

I'd design around the idea of notifications.

Users could pick which events they're interested in subscribing to, then indicate how they want to receive notifications by email. This way, you can accommodate users who want no notification, as well as those who want notification by email, digest email, SMS, RSS, smoke signals, carrier pigeons, and telegraph.

Ended up going with 2 settings that are changeable by the user:

Email me for any new root level comments       [X] On   [] Off
Email me for any new comment replies           [X] On   [] Off