Different people have different ideas of right and wrong, I get that, but there are some unwritten rules we all agree too right?  Perhaps, they're called common sense? 

I love a freshly mowed lawn as much as the next guy (that's mine pictured) and typically mow weekly.  Occasionally, life can get in the way and you have to go an extra day or two.  I guess my neighbor doesn't believe in stretching those extra days.

A couple nights ago, he was out STARTING to mow at 9:35pm.  Starting.  Now I do realize we have an unusually generous amount of daylight here (and the blackout curtains in my house prove this), but it's still 9:30pm.  Isn't that common sense/unwritten rule/common courtesy that you don't mow past, say, 8:00pm?
Am I crazy for thinking there are very few reasons it would ever be acceptable to be mowing at 9:30pm?

What are other things you would think people would "just know," but might not?