Topics are a hacky replacement for categories, IMO.  I'd
like to use topics for things like "refactor" or
"jabberpy-related" and keep categories for different
components of Hiss (plugin system, conversation system,
etc.).  I think the Bugzilla method for this is pretty nice,
where each component has a default maintainer, etc.

Seems like topics already are categories. You can display
the list grouped by topic, and edit your config to do that
by default. However that doesn't work well when bugs have
multiple topics: IIRC it makes a different group for every
particular combination of topics for which a bug exists.

Topics like "conversation-sys", "plugin-sys", etc. are
actually categories.  We should be able to specify a list of
categories associated with each bug.