Like, in a situation where there's a bunch of NTs, one of them makes some nuanced remark or question to you, and you put on the same face or "mask" as the others (reading the room, masking so far so good), then you retort with something that you can tell a second later was a non-sequitur, so your interlocutor repeats the remark or question, you're like "Uhh, yeah, ABCDE, that's a lot like VYWXZ, I hear ya, totally, but it could've been worse if IFYGSF." not answering literally, as you can "sense there's something", in their tone or face or posture, but you couldn't seamlessly put your finger on what the nuance is.
But then it hits; one of the others in the group says "he doesn't get it." You've been OUTED. They just spoke about you in the 3rd person, which is one of the first microaggressions that we tend to notice when we're "outed".
I've encountered that back in my 20s before my understanding and masking really improved (post-diagnosis), and all I could reply is something like "OK, you got me...I have to come clean that I'm not very good at reading between the lines, I feel kind of embarrassed about it but I didn't intend to cause any upset." I think at that point, you have less to lose by openly admitting your weakness, as it also shows that you're more alert to being possibly taken advantage of (as you can often tell there's something unspoken, but just can identify WHAT), and it shows you're not being passive-aggressive.