1. Highlight the message you are posting 2. Give it a color Ex: say I was posting "Hi". I would take the Hi and color it. You would then be able to post it.
You can also write a whole load of jibberish after your message and colour it white. Example; Hello! Jekejriejjsieorjjdje To see that I have written something as well as the hello, all you need to do is to highlight after the "hello" that I've written. You may also use any other bb code to bypass this, like colouring text (like suggested) or fonts like the one I'm currently using. God having your own server forums helps a heck of a lot.
Alternatively, you could add something constructive to your comments! A comment with less than 5 letters contributes nothing to a conversation.