Two commenters X,Y with sub-threshold karma (<1,000) could never have a dialogue (two-way, real-time) as a third party Z would need to endorse their each and every comment.
Two commenters X,Y (Karma 1,000+ each) in substantially different timezones with a-synchronous dialogue (eg, overnight replies) would need a third party z to endorse each and every comment (at least until the other wakes up).
Two commenters X,Y (Karma 1,000+ each) with opposing views, could never have a real-time dialogue without a third party z to endorse each and every comment (unless #)
Hopefully these are at least helpful to dilineate.
