Comment by jmyeet

"Ch" is a strange hill to die on. "Ch" has a mostly consistent pronunciation (eg chair, touch, chain, choke, recharge, etc) that no other letter combination does.

Exceptions to this are generally loan words, particularly from French (eg chaise, which sounds more like "sh"). Others are harder to explain. "Lichen" springs to mind. Yes it technically comes from Latin but we're beyond the time range to truly consider it a loan word.

There are also some "ch" words of Greek origin (IIRC) that could simply be replaced with "c" or "k" (eg chemistry, school).

"Kh" on the other hand I think is entirely loan words, particularly from Arabic. Even then we have names like "Achmed" that would more consistently be written as "Akhmen". "Khan" is obviously a loan word but I think time has largely reduced the pronunciation to "karn" rather than "kharn" if it ever was that.

But I can't think of a single "kh" word that pronounced like "ch" in "chair".

"Sh" doesn't seem to crossover with any of these pronunciations.