Dear Vladimir,

Many of the issues surrounding "apos" seem shaddowy
to me too.

On just a couple of matters I have a clear opinion.

 --- "apos" from sgml is a very convenient and expressive
tag; so (as I imagine we all agree) there is no need here
for further letter tag invention.

 --- since MODIFIER LETTER APOSTROPHE alias "apos" is
recognized as a letter rather than as punctuation
(diacritic) and in Ukrainian does indeed belong to the
spelling of words and appears in dictionary listings just
like "sftsn" or an ordinary letter, I believe "cyrapos" is
a better designation than "textapos". The latter would
suggest diacritic status.

Why not \apostrophe or \apos ??  The reason lies in the
convention that every cyrillic letter should in the TeX
world have a name beginning with \cyr or \CYR.

Of course there are still nagging questions. Should there
exist both \CYRAPOS and \cyrapos as letter status suggests.
There is no obstacle to this since one can "equate" them at
the glyph level. And unequate them if and when some
typographer decides to make a geometric distinction no
matter how slight.

Cheers

Laurent S.