Why is TAMIL SIGN VIRAMA (pulli) not Alphabetic?

[Richard Wordingham via Unicode]

On Tue, 29 May 2018 14:03:25 -0700
Doug Ewell via Unicode <unicode at unicode.org> wrote:

> In any case, Ken has answered the real underlying question: a process
> that checks whether each character in a sequence is "alphabetic" is
> inappropriate for determining whether the sequence constitutes a word.

Back in the second post of the thread, I made the point that a
conformant Unicode process cannot always give a yes/no answer to the
question of whether all characters in a string are alphabetic.

What we seem to have established is that Unicode properties are not set
up to facilitate the identification of words.  Given that
spell-checkers work, we have taken a wrong turn.  Perhaps we should
reconsider "b⃝e⃝", which consists of two letters each inside its own
enclosing circle.  The spell-checker I'm using considers it a
misspelt word, rather than two symbols side by side.

Richard.