Yeah the two times I was on a plane where people clapped it was because of less than great weather (like the runway being in a quarter inch thick ice sheet) and the other because air traffic control fucked up and told the pilot he was clear to land when a 737 was right below us landing already.

To be honest, both times I think I agree clapping was ok.

If you land in fine weather and no near miss, and still clap? That's a red flag