As Facebook has no official support I'll try my luck here to see if anyone knows.
No, I'm not a stranger, haha. But I have been in need of contacting people with similar names because sensitive e-mails meant for them keep being sent to me (first initial.last name@gmail.com) and I want to notify them of it. It's like 5 different people, who also have Facebook accounts and were easy to find. The worst thing I received was a PDF from, supposedly, one person's boss with sensitive numbers that said "DO NOT SHOW ANY EXTERNAL PARTY!".
The problem is, I never get a response. It never even gets read. It's not only these people as well, but also people I met at parties and I want to tell something through Facebook, but not necessarily add them as a friend.
Is Facebook hiding messages from strangers, or what's going on? I don't think I've ever received a response when I've messaged someone I'm not friends with, or have the messages read.