Hey there,
Well, the forum is a joomla extension called kunena:
www.kunena.org/
and the min. search term length is a restriction that they have imposed most probably for performance reasons. 2 characters search would probably return too many matches and won't be usable... Will stress the database server etc.
As a workaround you can always search google with
site:compojoom.com/forum k2
About the real problem. 2 possibilities
1. You have a javascript error on the page and that is why you can't see the comment form. Right click on the page and select inspect element. Then change to the console page. Refresh your page. Do you see any error related to the comment system?
2. in K2 you can configure the comments in the global config, in the category config and in the single item config. So if in any of those locations you've set to "don't show comments" the comment system won't be invoked. The easiest way to see if the system is at all included on the page would be to right click on the page -> view source and then search in the source for comment. Do you see something with com_comment? If yes, then the comment system is being loaded and you are most probably being blocked by 1.
If you give me a link I could also have a look and let you know if it is the first or the second possibility.
Regards,
Daniel