@replies and reply id's

[elaverick]

What's the link between the @reply and the in_reply_to_status_id.  Am
I right in thinking its the Twitter site that links up the @reply
nickname to the desired status/user id?  What happens if you post a
reply with only a partial link up in place ([EMAIL PROTECTED] in the Tweet
but no status ID in the XML or vice versa)?
I want to try and keep nice and compliant so I want to know how much I
have to enforce in terms of replies.