That’s one of the reasons that I don’t - with rare exceptions - do pm’s on discussion forum platforms.
I feel the exact same way Matthias. I remember when they would a DELETE this conversation button in the PM's whereas now there is an END this conversation button. I am guessing there had to be a LEGAL reason for that change. I wouldn't believe anyone who told me otherwise though. Your information (whatever you volunteerly give up is a commodity). Even Christian forums get bought and sold off (which sale would obviously include all the data collected on their members). Voluntary contributed ofcourse.
I heard something to the effect, that data collecting on your vehicle (from inside it) is used to find reasons to charge the car owner more on their insurance. Sheesh, can imagine the traps of searches for something like a symptom you might be having, not to mention thinking you are privately sharing the same to another, and how you could have possibly helped to exclude yourself from health coverage in some way? Things like that. I don't pretend to know how it works (but that its in secret, and without your consent for the most part) and ends up being for their gain (and your loss) in the end, because its definitely not for our benefit.
Thats why I try to stay with the word of God only and keep it as light as possible online also.