Rules is superb! -pause- Is there an existing solution(rule-action or token) to send e-mail to:
a) Anonymous commenter (mailing to created comment author returns "Unable to send e-mail..." warning for anon. commenting).
b) Thread participants or the "rest of"(other than comment author and/or content author) participants. Thread may be whole or parent + siblings + children comment.
c) Author of parent comment (if it is a reply to an existing comment).
We are missing the subscribe/unsubscribe option with this approach. But I'm not sure if rules can handle something like that, since I haven't yet played a lot with it. Not an issue for me as of now. Also, I'm not aware of any existing discussions regarding making rules as a replacement for comment notifications.
So.. if there's no good solution for at least point (a) and some of (b), I'll build one :)