This is important. It is not always necessary or appropriate to try to maintain the secrecy of otherwise public, directory information (like email addresses). Unless you are, say, FetLife, it doesn't actually make that much sense to hide the fact that [email protected] has at one point signed up for your service.
On the other hand, associating [email protected] with posts he thought were anonymous is an enormous violation.
This is important. It is not always necessary or appropriate to try to maintain the secrecy of otherwise public, directory information (like email addresses). Unless you are, say, FetLife, it doesn't actually make that much sense to hide the fact that [email protected] has at one point signed up for your service.
On the other hand, associating [email protected] with posts he thought were anonymous is an enormous violation.