Sorry it took so long to get back to this.

At the time, I suppose I didn't realize they were only pretending not to understand. Particularly with my brother, I honestly thought I just wasn't making myself clear. Now I know, that's just exactly what he wanted me to think, so I'd give up trying to express my opinion and get down off my soapbox. If I "can't" explain my position adequately, then maybe I'm full of baloney after all.

He knew perfectly well, all along, the point I was trying to make.

I do believe that pretending not to understand what I mean is a form of weaponized incompetence. It doesn't seem to me that my brother was looking for a fight so much as he was trying to get me to shut up. In either situation, whether pretending not to understand, or pretending not to be good at doing the chore, the goal is to silence the other person.