I would think you could remove quite a few leaves from a well established Heuchera plant without killing it. Very often the outside leaves on the bigger plants get spotty and discoloured and worn out. I remove them as I am on patrol deadheading etc. Heucheras are pretty tough. It is usually damp that kills the middle of a plant. There is usually a surviving sprig that can be grown on and make a good plant later.

Grow Heuchera 'Obsidian'. Black spot won't show then! Phil J