Hang on; Imposter Syndrome would mean that you would come across as a fallible, non-expert, since you believe yourself to really be an imposter. Do you really mean something like the Dunning-Kruger effect, which is sort of the opposite of Imposter Syndrome, people with little knowledge believing themselves to be infallible experts?
Impostor syndrome means that the person thinks of themselves as a fraud, not that other people do. So someone dealing poorly with impostor syndrome might well only chime in when they are exceedingly confident, or only when they do research and can be certain that the information/position they are providing is correct. If you keep your mouth shut except when you're 100% certain, you'll likely look like an "infallible expert" because you're always correct from an external perspective, even if you are quietly filled with self-doubt.