I'm not talking about just the optional text fields here, which already have some decent builtin privacy controls anyway. I'm talking about things like the stuff on the Statistics tab that you simply cannot currently hide, which has info that you didn't populate, it was gathered anyway. It's not a big deal, but it's also doable to allow some control over it, whether it's just a new dropdown on profile privacy for the Statistics tab or something more granular, allowing you to hide things like Username History or your "Last Activity" from public viewing. Maybe even allow hiding of the Emblems tab so that if you have a ton, you don't have n00bs going "I WANT <insert non-requestable emblem> LIKE <some random user> HAS!"
We all know invisible mode is kinda useless if you want your non-staff friends to be able to see you online. XD