So, the term "micro-aggression" is almost certainly one of those things someone somewhere came up with in a paper that some undergrad seized and started using vernacularly and it's truly an abomination of communication.

Because what it is - what it actually *is* - is so much worse, and more simple, than what it conveys.

It's when someone who knows better, who knows what the boundaries are, repeatedly violates them in small ways to test if you'll continue to enforce them.