On Fri, 05 Nov 2010 08:45:27 +0100, Sebastian Spaeth <Sebastian@SSpaeth.de> wrote:
> One UI improvement I would love is to see the number of unread 
> emails in a thread in notmuch-show view. I often reply to a 
> mail in a thread just to see that there are followup mails that 
> resolve the issue already.
> 
> If I had seen that there are more unread mails in that thread 
> (or at least that branch of the thread), I would read those first 
> before hitting reply.
> 
> What do others think?

Hey, Sebastian.  Try looking at notmuch-search-line-faces (not very well
named, my fault) which sets the face of search lines based on tags.
I've been using the following setting:

(setq notmuch-search-line-faces
      '(("delete" . '(:background "grey8"))
	("unread" . '(:weight bold))))

Threads with unread messages show up in bold, which makes them pretty
easy to identify.  I also bind a key to filter

"tag:unread and not tag:delete"

which allows me to easily pop view the unread messages.

jamie.