Hi Eisel,

I don't think I've ever seen a retroflex ".n" changing to a "~n"
before "h". I wonder if what you're really referring to is the
"niggahita" (.m) changing to a "~n" before "h" as in, for example,
ta.m hi > ta~nhi. This is covered by Kc 32 as follows:

32, 50. ehe ~na.m.
  ekaarahakaare pare niggahita.m kho ~nakaara.m pappoti vaa.
  paccatta~n~neva parinibbaayissaami, ta~n~nevettha pa.tipucchissaami,
eva~nhi vo bhikkhave sikkhitabba.m, ta~nhi tassa musaa hoti.
  vaati kasmaa? evameta.m abhi~n~naaya, eva.m hoti subhaasita.m.

The rule states that the niggahita can change to ~n before e or h. It
is my understanding that the examples "ta.m hi" and "ta~nhi" are both
pronounced the same -- the difference being only in the spelling. But
I'm not absolutely sure of this. It should be noted that Pali does not
have the combination -"nh- (see Sadd III 609,3).

Jim

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