Even though there is no widely accepted agreement regarding the difference between knowing about someone and knowing someone, that difference is frequently implied in the fora when members write such things as, "Until you meet someone face-to-face, you can't get to know him/her."
Certainly you could argue that often something such as having a bad-temper fits into both categories, but, for this discussion, let's say that the "know-about" items are those things that you could discover without meeting somebody directly. It should be added though that, just because something is discovered through a direct meeting, does not automatically make it a "know" rather than a "know-about"; e.g., if someone reveals during an F2F that he/she travels a hundred days per year, that is still a "know about" matter, not to mention something you'll probably "knock about" before seeking further contact.
Many, many questions can be asked where the experience of knowing about somebody and the different experience of knowing somebody would be one of the aspects involved. I'll pose just one of those inquiries, "In those cases, where you chose to stop seeing someone, was the decision based more often on a "know-about" or on a "know" issue?
Testing whether the No-No's come from the "knows" or the "know abouts" & hoping not to hear, "The Yeas have it",