Currently, the search function is limited to thread titles. Also, several D.O. customers have complained in the past about not being able to subscribe to a thread that interests them or in which they've posted a question.
I've been a member of a few Google Groups: Vagrant; Puppet-users; Foreman users; SOGo; for a short while and it's been nice being able to search old threads (in their entirety, i.e. not just the titles, whenever I have a question). Most of the time, I'm able to find an answer w/o needing to actually post my question.