I believe I share some of Kylie's concerns about private messages. I get way too many emails slugged with the subject line "Your page on WikiTree," indicating that the sender was on my profile when they sent the message, with text something like "My records indicate that Thomas Abbott's mother was Mary, not Hannah" (no indication anywhere of what profile the person is commenting on or asking about). These kinds of messages might respond to a profile message I posted somewhere once upon a time, or maybe they are about a profile where my name is listed as a manager, or maybe I am getting the message as a leader of a project that is a manager of the profile.
I don't like having to send email replies that say "I have no idea what you are talking about" and I find it very difficult to organize an email folder that's full of messages from noreply@wikitree concerning "Your page on WikiTree," so I wish there were additional mechanisms to ensure that the subject line for a message provides more clues about the actual subject of the message.