On Apr 3, 2011, at 10:34 PM, serialhex wrote:

>  ruby-talk magically knows where your posts are supposed to be :P

Not quite magic, just the 'In-Reply-To' and 'References' email header.

http://tools.ietf.org/html/rfc2822#section-3.6.4

More on the subject of message threading, courtesy of Jamie Zawinski:

http://www.jwz.org/doc/threading.html