Few months ago I've started developing a web-site with a goal to provide some help to newcomers in programming.

http://codeabbey.com

In its core it is a collection of programming problems - to solve them users should write some code, process random input data and submit correct result (so it is result which is checked).

After a while I decided it would be useful to allow people to see each other's solutions - of course only after the given problem is solved by this particular user - so one can learn something comparing other's code with one's own.

Later I came to idea it may be useful to allow comments under solutions, so people can write some messages pointing out potential problems or disadvantages etc.

This functionality was added only few days ago.

As you see, I'm a bit slowpoke in inventing features to my site. So I would be glad to be hinted with more ideas about things to be probably added to it.

For example right now I have no clear idea how to popularize comments system just implemented. Probably commenting should give some "compassion points" to user and some tasks should require spending some of these special points for solving. Not quite sure it would be good.

Thanks in advance for all your hints, advice and ideas.