Is artificially modifying one's self ipso facto a bad thing? What's your basis for this claim?

I find it extremely doubtful that you can actually give a definition of "true self" which meets the following conditions: 1) coherent and non-contradictory, 2) in accordance with reality, and 3) something a person should care about preserving.

I find it even more doubtful that you can give a definition of "artificially modified" which is meaningfully distinct from natural change.