I remember seeing that message before. It definitely seems to be when messaging multiple new people and it reset pretty quickly. Seems like you'd have to be messaging quite a lot of people to even see it. Although I understand that number is lower for new users with good reason. I think it's fine how it is and that patience is a virtue. Another similar message I recall seeing was when there was a new user and it said something about them receiving a high volume of messages so to try again later. That too seems pretty reasonable.