I don't say anything. I have 588 days of playtime and have done over 5,000 raids and trials with who knows how many regular dungeon runs. I genuinely cannot be bothered anymore.

I've actually had people threaten to kick me for not greeting them later on in the dungeon, too. I'm almost always the highest DPS (when on DPS) in the party and play every job and role very well, so it was pretty bizarre when it happened with nothing going wrong. Some people seem to think something is wrong with a person that doesn't say hello at the start.