I think this is fixed with r27647, but let us know if you see this bug again.
I'm not sure. The former seems safer to me (if there's a combat skill that also affects modifiers) but less efficient.The other part of this is that (when it's a combat skill) sometimes we fire "addAvailableSkill" and sometimes "addAvailableCombatSkill". The former recalculates modifiers and the latter doesn't. I am curious as to whether we could just always use the latter.