[Users] Sort by thread length?

[MJ Ray]

Does anyone know a way to sort a mailbox display by thread length,
please?

I'd like to make it easier for me to spot lone requests that haven't got
bogged down in long discussions. Searching for mails with empty
in-reply-to header doesn't cut it because that finds the head mail of
every thread.

Scoring replies up and then sorting by score doesn't work because
sorting thread views only looks at the score of the first mail, rather
than the total of the thread. I don't see how to make an email be
sorted by the sum of its replies' scores, which could help.

Is there some clever way to do this?

Thanks for any tips,
-- 

MJR http://mjr.towers.org.uk/
Member of http://www.software.coop/ (but this email is my personal view
only)