I'm not a moderator so I can't really tell you what you can or can't do but general guidelines seem to be those of general courtesy to your fellow disers.
I know that no bad language is allowed. The powers to be would prefer you not using text messaging language. Other than that you can do what you want. If something you say is objectionable they will pull the thread from the boards.
As far as people being nice on the boards-well, there are some extremely nice people and there are some that seem to object and complain about everything-but you will find that on most boards.
Overall Dis is a board full of wonderfully helpful people. Our moderators are the best!
Have fun with Dis!