@Pepijn Sweep,
I have already said I did not and do not read your PMs (serious, I don't even read all mine, ask some of the many who send angry replies about how I ignore them).
What happened was that I received a templated-looking invite forwarded to me as spam from someone who did not even know
Salima.
I queried the database for a count where text like "%PM string here%" and it returned something like 580 results. So I deleted them.
I did not read anyone's messages unless they were forwarded to me. I asked for more to be forwarded to me and received more.
Theaetetus had sent some too, but the count when I queried for them was not large (dozens maybe?) so I left those intact (inviting your friends is one thing, spamming hundreds of people is another).
I have better things to do than snoop on people's messages here but spam, and other threats, scams (today someone else also told me about someone asking for money to two different accounts) etc are supposed to be reported to us (we'll make an easier mechanism to do so, we used to have buttons on PMs to do it but for now it will have to be copy paste) and when they are I simply query the database for the text I already have to confirm it's existence (otherwise you could falsify a report) and will delete in cases of mass spam.