Hey all. It looks like a lot of people dont know how to start PMs from mobile phones. It is a bit of a pain, but it can be done, I do it when I'm in bed with my phone and I just dont want to turn on my PC to do it.
from your mobile phone, once you open the the forum, you will see a dropdown arrow in upper right. Click it, and switch to classic version. From there the forum looks the same as on your PC, you know how to start a new message. The drawback is that the PC version is not android optimised and it doesn't communicate very well with objects that have separate scroll down from the main window, causing me to not be able to fully read what I wrote sometimes. So keeping PMs short is the best way to go.
To switch to mobile version, you must go back to home page first. Since there is no mobile version of PM, trying to switch back while in PM mode will not work. Once you are on home page, scroll down, past the banners, you will see a few options. The one on the far right is "mobile version". Click it, and you are back in mobile mode.