As for the current situation, if the ex noticed all the flirtatious comments I was making and felt threatened, he probably wouldn't confront me directly. He'd probably do what they guy in the above example and several others have done; make a point of ignoring me at first and subtly trying to provoke me, and when that doesn't work, confront me directly later.
If this is what that guy was doing, it seemed likely he'd become a bigger problem later. At the time, I did not feel a need to confront him. If he became a bigger problem, that might change.
You're doing it again. All this and more about a guy that apparently you've never met personally, have never even seen in person to observe his behavior, and have never talked to. Yet you're pretending you know how he thinks and acts based on your experiences dealing with other men.