I have the same problem myself. I'll probably implement a bit of browser detection and turn off the advanced editor for people browsing on iPhones.
It's kind of a pain, but you could go into the forum preferences section and turn of the advanced editor in your settings. That should let you post.
Edit: Nevermind, I just realized that setting isn't live yet. I have it running in the current beta build. I'll try to get that up this weekend.