I'm not sure whether that is intentional or not. Maybe you're supposed to have some control over your visitor messages. Or maybe it was a leftover artifact of the past.
Funny story: when the visitor messages feature first came out, users had full control over them, and you could even edit them (as long as they were posted on your profile). So you could change people's messages on your profile to whatever you'd like. I had a little fun with that before it was removed.