Most Helpful Guy
Check the G@G Community topic.
There are tons of questions in there about the recent updates gone wrong that GAG laid upon us. This is one of them. Now if a question has no activity for 48 hours or if it receives a MHO for either gender, it's now automatically closed to further comments.
Most Helpful Girl
The new site update does not allow you to do so after the question has been closed. The question is closed after you choose a MHO.
See this My Take for more about the site updates: