This post reminded me of this thread. It seems like this kind of thing comes up a lot: I think of a “detour” as the action caused by a “diversion” while in American detour is also the thing.
Another one that has come up a lot for me recently is that to me the phrase in-between brackets may be parenthetical, a parenthesis, but the brackets themselves are brackets. To an American, the pair of brackets themselves are called parenthesis. So you have “parenthesis” marking off a parenthetical phrase, or maybe even something that isn’t parenthetical, which I find deeply weird.