Custom in what way?
I think it would be pretty easy; the only hassle would be that sometimes the discussion form is loaded without a category pre-selected.
So adding extra fields when you create a discussion, like the predefined user info extension. I suppose that could be used as a basis, but where would it put that info in the database?
I looked at the database and I think for something like this another column would be needed in the lum_comment table, a simlar setup to the Attributes/Preferences field in the user table. That way you could assign as many bits of extra info as you like, might be useful if someone makes a poll extension as well.
It could create it easily? The question is whether it's best done in the core. Would it be such a bad thing if all (or some) of the tables had a sort of miscellaneous column which could hold custom values like the user table has?
Comments
I suppose that could be used as a basis, but where would it put that info in the database?