A lot of people are having trouble replying on WAP. You cannot see the quote, and the post button seems to be unreachable most of the time. I have a work around that's never failed me yet.
Here's the secret to success:
When you hit reply, press any character till the quote is visible.
Delete the character('s) you had to type to see said quote.
Press the trackball once, and scroll down past quote and type your response.
Press the trackball once, hold the shift key, highlight the entire text in the box using the trackball.
Press the menu key and select copy to copy your response and the quote.
Use the back key to get to the normal reply window, one page back. Should take 2 presses.
Press the menu key and paste what you just copied into the normal reply window.
Don't worry if you don't see anything in the window, sometimes you do, sometimes you don't.
Now you can get to the post button and voila.