Ok, I am lazy I haven't checked if this has been suggested before....
When a new thread is opened and a question is asked by someone allow them to turn off commenting on their thread. This way, the thread doesn't get hijacked from another member for another question. I've seen this a lot of times.
Or even better: As soon as an answer is marked as "Solution" by the thread opener the commenting should be stopped. There is no more need for comments if the right answer has been given.
This way people also think more often about accepting answers as solutions and so threads are getting marked as solved. For us who check the new threads every day we save time because we don't have to go in.