This is interesting, because I have the same things happen with different reasons behind them. Responding to a joke as though I didn't understand it was one is something I find internally amusing, and my own sense of humor is pretty dry/deadpan so people do miss sometimes when I'm "joking back" as it were

I think the dividing line is the intensity/frequency, unless one knows one is diagnosed. My coworkers for example pick up on the differences in the way I talk when I'm joking vs sincere pretty quick, and likewise learn that I find some small amusing in being irritating now and again