Someone above you tells you you did something wrong or poorly. Your first instinct is to believe because you implicitly trust their authority. You might do some homework and are like "wait a minute, no, I actually did this right." Then you might look for other reasons. "I did the thing right." So THEN you start looking at the communications, where did the boss get this idea? Now I need to fix THAT?
The boss responds, and the follow-up you gave gets NO RESPONSE. Instead, as if you had said nothing at all, the boss makes a severe move and orders you to work differently.
What is going on? THAT doesn't really line up either. Literally trying to do that move is worse.
And after some time you begin to Occam's razor your way into the truth.
The boss is clueless and/or incompetent. Or just doesn't care. Either way, they're the impostor, not you.They recieved some small bit information in your space, and it sounded bad to them, and they just dumped that issue on to you -- with a combination of any of: a lack of intelligence, a lack of good information, their own fear, and the ability to make it your problem.
This is purely hypothetical and absolutely did not happen to me of course. Nope. :)
It sounds like you're saying that someone else is making you (the receiver of the advice, not you, jrm4) feel incompetent. How are they doing so? Shifting the blame for their own incompetence? Trying to push work on you that really should be their work, but they can't do?
And, how would you detect this? By realizing that it shouldn't be your work? But that takes knowledge of how the organization should run that a person with imposter syndrome isn't likely to have. Even more, isn't likely to be confident that they have.