Hi there, thanks for the link. I am finding artifacts with your file even without any denoising also. May I ask where the mesh came from? Was it download or sculpted by yourself? I ''tried'' the following to eliminate the artifacts:
1. Deleted the phong tag and replaced it with a new one.
2. Went into points mode, selected all points and used the ''optimized'' command.
3. Enabled the Subdivision Surface modifier
4. Changed denoising mode to ''Corona high quality''
5. Set a noise limit of 4 and let render.

I hope that helps.