Sorry, I think you missed the point. As mentioned in my post, my parents' neighbor who chooses to mow at 5pm on Saturdays is retired. He has literally all day every day to mow the yard, yet chooses to do it at 5pm on a Saturday which is prime time for any working person who wants to entertain company or simply relax in their yard. We scramble to do our yard work during the week or early on in the day so we can get this time to relax. Out of simple respect for the neighborhood, he would do the same. Of course it's not late and he's not doing anything wrong, so we're certainly not in a position to say anything to him about it. I don't have an "expectation" of silence during daytime hours but I do have an expectation of common sense, common decency, common courtesy, and neighborly respect.
In the case of my parents' neighbor, he's just an airhead and doesn't even realize it. In the case of most other people, including OP's neighbor, I'd suspect it's out of spite. Either way, OP and us are not in a position to say anything about it.