Why comments are not condisered "activity" for a question?

edit

I find activity sort in this web site very useful, in fact it it the default sorting for questions if you just go at http://ask.fedoraproject.org

If somebody add/edit a quetion/answer the post is immediately considered under activity (which is true), and consequently you will find it higher in activity sorting results. This is not true for comments.

If you add a comment to any answer/question there is non change if you select activity sorting.

I do not know if this is by design but in my opinion also if a comment is added/edited in a post we should consider the post under some kind of activity and it should be ranked higher if activity link is pressed.

Don't you agree?