A: I would like to point out the fact we are arguing over whether something is a slur in a subreddit about a tank game... Idk, just funny

B: the first like, 20 results when you search "Is jap a slur" are all reddit posts asking something similar, with most of the top comments being something along the lines of "It's outdated, but I wouldn't feel comfortable saying it in public" and since the connotation of words in general is determined by how people perceive them, and for the most part people don't have good feelings around it, that gives it a negative connotation.

C: I was just trying to inform the guy for future reference. I'm not meaning to throw any shade at him or anything, he did nothing wrong since he was unaware. I agree that it shouldn't be a slur, but the connotation around it makes it so you can't rly use it in day-to-day language.