[smegel]

OK I know more about C# now than I ever planned on knowing.

The problem with OP comment is that KISS and premature optimization are not diametrically opposed. Thet are two separate principles that mean different things.

Premature optimization is bad, but not because it necessarily violates KISS. Similarly, many people overcomplicate code for reasons nothing to do with optimization.

His argument reminds me of people who argue against free speech generally because we already ban people shouting fire in a cinema.