Unfortunately there is no way to view post count from the mobile site. We try and keep it optimized the best we can and some things have to be left out to get the best result.
When you get an email from a thread you want to unsubscribe from scroll down and there is an unscubsribe option. Be careful though there is another option right below to unsubscribe from all threads.
You can also access your user control panel and do it that way as well. To access
That click on the user cp option at the top of the mobile page.
Posted from my CrackBerry at wapforums.crackberry.com