I was also thinking it'd be interesting to have a heat map that showed clusters of threads with active, lively interactions around the same topic, rather than only individual thread content.

More threads with a structure like

OP
A
  B
     C
      A
  B
     D
         A
         C
            D
 E

Instead of with "GM structure"

OP
A
B
C
D
E 

 First one had indentations, to show nested replies. Sorry.