There's no reason that people who post there can't also discuss here.
At least the bugtracker has some form of structure, otherwise the same
topic comes up again and again in a 2- or 3 month cycle. Knowing what
is a priority, what isn't, what is out of scope or just technically
impossible can be tracked and looked up in a bug tracker; there is no
way to do that with a mailing list other than read all of the archives
and somehow make a mental for yourself of topic to get an idea of
where things stand.
Of course a bug tracker needs to be maintained a bit, having the
duplicates deleted or merged, completed things marked as such,
suggestions need to be either 'never', 'someday', 'soon', or whatever;
it seems like Andy's tracking that quite well. Maybe the anonymous
posting can be turned off, there's always improvements to be made, but
a structured process is much better than 'fire an email to the list
which then promptly disappears into the void'.