One conclusion I've come to is that each case needs to be looked at individually. Tedious as that may seem, it kind of goes with the territory when you're talking about respect.

It makes sense to me. The appreciation/appropriation example I've used whenever I've had to explain the distinction is: if I invite non-Jewish friends to a Seder, of course I expect them to participate; they are guests and they are welcome and if they bring wine or some kind of properly kosher side dish, that's very thoughtful, and if their youngest child wants to ask the Four Questions, the kid should go for it. If they go off and next year—while still not being Jewish—decide to host a Seder of their own because they think it's just so lovely and meaningful, we are going to have words. [edit: this is a real-life example in that I have heard of it happening; it has never happened to me. I like to think this is because I do not invite people to my family Seders who are jerks.]

This doesn't mean that there are no ways to be offensive in Japanese culture. For a selection of ways to do that, I give you the example of Logan Paul, whose career has just ended as a result of it.

Yikes.