Hard disagree.
1 Data breech and digital housing creates a massive lawsuit.
SE already has tools in place to determine if the character is on the same service account as another.
And yes "Muh privacy" is a very valid argument; unless your going to give a sane reason for violating peoples right to privacy.
Honestly as far as investigating plot issues - I suspect in 1 day a GM can probably check every plot on a world and determine how many plots are owned by the same service account - so the only reason they have not done anything is because they choose not to.