Re: Introductions
The only way to achieve all this with current feature set is through a User Tracker, which can allow comments (if you set it up to allow them), replies, notification of the author of the tracker item, shown at registration time, etc.
To get you started, apply this profile in a tiki for testing, and you'll see how it is configured:
http://profiles.tiki.org/User_Trackers
You can also do all by hand. You can read the documentation about it:
http://doc.tiki.org/User+tracker
Cheers
Xavi