You know what would be really cool? If I could submit a support case without getting the absolutely unhelpful "your post couldn't be submitted because of invalid html code" error.
First - why is it...
Thanks for taking the time to bring this up and for managing to find the cause of it.
Interesting though that it won't let you post with any formatting. So it actually uses the same editor as what's on a normal post. Can you post with any special formatting?
I have to admit the error isn't that great, I have brought this to our product team recently and going to work with them on looking on ways to make it better so it actually tells you why it's presenting you with an error :)