I can tell the difference, at least with simplified hanzi vs kanji, most of the time. When I was in Japanese language school, a lot of Chinese students would end up with small mistakes in Japanese as there are some other fairly minor writing differences. I can’t remember if it was that Japan was more strict or the writing was taught slightly differently.

Across language, there are some fun coincidences in completely unrelated languages that have words that mean (nearly) the same thing with (nearly) the same spelling, though of course I can’t conjure one from the depths of my not-yet-awake brain; I’m sure wikipedia or something. I think ‘Interlingual homograph’ is the term related to those. I still like Japanese letter (手紙 lit. hand paper) -> Chinese toilet paper and other fun ones in non-alphabetical scripts.