As long as your post contains
more than just a "yay, first post" comment.. It's not technically against the rules..
However, most forums I've been on, ppl wonder why one even takes the time to type it out

Could just be me though, but I don't see the point in it.... (gawd I sound like my grandfather.. hehehe)...
Just make sure your posts have a little substance moreso than "yay my first post, this "wahtever" is kewl! Awesome!!!!11!!1" and I'm sure no one will have problems
