if room comes to a state where last person stopped speaking,
then setting room to clean state is logical,
next person to start speaking is the only reference point
setting marks for all levels between current speaker and next speker (on
conversation level raise)
and for 'count from' - check higher levels for a mark for potential use
so that 'extend' raised to 'meta' would still count 'next topic' as
going from previously 'extending' person
now going down by many levels - starts from marked person due to 'count from' logic
that uses marks from higher level if current level doesn't have a mark
but also going down by 1 step keeps the marks until we return to initially diverged
conversation layer
efim