Today, for the first time since I've owned it (115k miles total, 89k by me), my manual H3T engaged Hill Start Assist. This is an incredibly pointless and annoying feature for an experienced stick driver, so I wanted to know if anyone knew how to turn it off? I have never had it engage before, and the first couple times that it did, I thought my clutch was starting to slip...

 

You can't disable the Hill assist on any 2009-2010 H3/H3T.

The only way to engage it is to press the brake pedal all the way to the floor and hold it there.
If you have to press the brake pedal all the way to the floor there may be an issue with your brakes.
I have never had to press any of ours all the way to the floor to stop or hold the vehicle even on the steepest of inclines.