Account: rtk
Character: Amthus Duval
Having tested this against another PC and successfully stealing 4 levels (tried it twice) it applied no bonus BAB. I tried attacking as well just to make sure it wasn't just an error in the character sheet but definitely didn't apply the bonus.
I tried this a second time just to make sure, and it's definitely not working.
In addition to the above the second part of the level 8 perk doesn't work, the negative spells do not remove negative energy protection