Distinguishing COENG TA from COENG DA in Khmer script

[Richard Wordingham]

On Wed, 24 Jun 2020 21:22:25 +0200
Kent Karlsson via Unicode <unicode at unicode.org> wrote:

> (Picking a quote slightly arbitrarily here.)
> 
> > They are supposed to represent subscript DA and TA, and for the 
> > old-Khmer style those look different. The fact that they look
> > identical does not mean that you should only use the subscript TA
> > and expect it to work where subscript DA is intended.  
> 
> 
> I know it is very late to say this but… To me this seem very much like
> there has been an ORTHOGRAPHIC change over time (preferring
> TA over DA when subscript), NOT a commonisation of glyphs.
> 
> Indeed, one can well argue that giving COENG TA and COENG DA
> the same glyph violates the character identity for these characters/
> character sequences.

The identities of the subscript consonants do seem tied to the base
consonants; there have been some drastic changes as the current shape
becomes too confusable.  Now, the usage of the base characters isn't,or
wasn't, as sharply defined as one might hope.  There are, or were (my
source is pre-Khmer Rouge), some words written with a base consonant TA
pronounced as though it were DA.

According to Huffman, there was free variation between what are encoded
<NIKAHIT, C> and <MO, COENG, C>.  By that correspondence, simply
abandoning the concept of COENG DA probably wasn't an option.  Deciding
to make COENG DA identical to COENG TA was an option.

Richard.