It seems that pain and irritation in the anus is often caused less by anal fissures and hemorrhoids alone than by damaged skin in the anus and rectum. This interesting video tracks the problem, and suggests one crucial measure that can possibly help. https://www.youtube.com/watch?app=desktop&v=lOwr94vVZFI

This is interesting. I also think using a sitz bath too hot can dry out the skin down there and make it very irritated. I use shower and then sitz bath after every BM, and even though it's so nice and soothing to feel the very warm water, I've often thought it might be having a not so good effect too on the very delicate skin down there.
I'll be trying his suggestion of no wiping at all (!), and maybe use a barrier cream like sudocream.
Can't hurt to try these things!