Re: Why havent they fixed jumping/mounting stuff?

I don't know, but to be honest the most likely reason is the process of reproducing the bug, which is pivotal when it comes to creating a fix for the issue - unless you find a 100% way to get it every single time, fixing it can bring some... interesting side effects (aka new bugs).

As far as I'm aware, the bug tracker currently has registered 4 different issues related to vaulting and their status is 'Confirmed', which basically means that they know about it. That's all I can really say.