As far as I know, there are 3 'threaded comments' plugins:
http://www.meidell.dk/blog/archives/2004/09/04/nested-comments/
http://www.scriptygoddess.com/archives/2004/06/03/wp-subscribe-to-comments/
http://weblogtoolscollection.com/archives/2004/05/09/threaded-comments-hack-for-wordpress-12/
Are they mutually exclusive, and if this feature were to be built into WP, would that also be exclusive ?
What I mean is, as I use the TC from weblogtools, and I change to the one written by Brian Meidell, would comments that have previously been made as threads revert to the normal format ?
And if WP came with it's system, would that also render the plugin threads as normal comments ?