I've just come across this question on SO: Implementation of achievement systems in modern, complex games
I want to expand on it with an "extra" question, and so I've added a comment. However, the question does not reactivate itself (stays on "active 5 months ago") because of my comment. Earlier today, I could not get a question to get reactivated by commenting on an answer.
I believe this used to be different, with any activity except votes reactivating the question. My alternatives seem to be to offer a bounty but that's overkill, or make an edit which isn't necessary at all.
What can I do? And why don't comments re-activate a question?