Comment by ziddoap

If you intentionally post something publicly, it's public. Full stop.

The tricky part is dealing with inadvertent or malicious (i.e. some other party), posting of private information to a public space. That's really hard to deal with on multiple levels.

For one, the archives would retain the information and scrubbing it is effectively impossible.

Secondly, legitimate things which should remain public (i.e. were posted publicly, are of public interest, etc.) can be argued to have been inadvertently or maliciously posted. So you need some way to moderate and create rulings for each individual case, which quickly becomes untenable due to the sheer volume of information being posted and the inordinate amount of time required to investigate vs. post.