You could simply kill two birds with one stone by having a checkbox that says 'This hack complies with the rules for posting hacks' or something like it :-p they need to click it to post a hack, takes milliseconds for real coders to click, and itll hopefully make accidental posters think twice. you could make it complain with javascript, much like missing a title, to pop up a box. not only will this alert people that those forums work differently from the average thread, but also better leverage for disciplining users should they NOT abide by the rules for the hack they post

and of course a minor server-side check for those who turn off JS.