You can certainly buy the soap add-on for the bidet, but the water works fine to remove the capsaicolin; your anus is a mucous membrane and secretes mucus and sweat, and when you wash that off, you wash off the capsaicin and your own mixture of fluids.

Ask questions rather than making assumptions.

As obvious as it is that washing crap off of you with water works better than wiping it off with a piece of paper, bidets work better than toilet paper.

You’re still feeling that tingle burning after you used toilet paper, so you have not actually cleaned off the capsaicin or your fecal matter properly.

You’re caught in the paper smearing tradition.