> That's all fine (in theory), but the only practical purpose of
> all that is to sort them on the web page, by severity first, then
> priority. If you browse the page of unassigned bugs for a category,
> you'll see that non-critical/high are listed beneath critical/low.
> Of course volunteers can work on bugs in any order they like.

Looking at http://www.netbsd.org/Gnats/category/toolchain.html we see all 
the high-priority toolchain bugs first, then the medium priority ones, 
then the low-priority ones.

That makes sense to me.  High priority bugs are the ones the project has 
deemed to be more important to address.  It doesn't matter that there may 
be a critical bug in a lower priority category.

> Of course volunteers can work on bugs in any order they like.

Certainly.  Opensource project management is often said to be like herding 
cats?

R.