See that menu across the top of the thread. Hit the arrow beside thread tools and select subscribe to this thread. Not sure if its the same on the mobile site. that is how its done on the pc version
There is no link for it on mobile sight. If you go on the full site on a computer you can go to user control pannel and set to auto subscribe to threads you post in.
Other wise there is a link at the bottom of each crackberry page "return to default view" that will load the full site on your BB
Posted from my CrackBerry at wapforums.crackberry.com