common practices in descriptive "grammars"

[RonButters at AOL.COM]

In a message dated 8/4/2000 11:42:17 AM, zwicky at CSLI.STANFORD.EDU writes:

<< ... scarequotes are quotes (that is, quotation marks) used for one of
their legitimate functions; the name "scarequote" denotes both form and
function. ... >>

In a message dated 8/4/2000 11:32:12 PM, laurence.horn at YALE.EDU writes:

<< Both are vernacular practices, not authorized by prescriptive grammars or
attested in most descriptive ones, but (for better or worse) neither is
particularly rare in the English-speaking (or rather English-writing) world.
>>

I realize that we are talking here about punctuation, which is normally not
much discussed in "descriptive grammars," but even so doesn't it logically
follow from the above that "descriptive" statements that ignore commonplace
linguistic practices are failing their descriptivist duty? I'm a little
confused when linguists of the stature of Arnold Zwicky use--even if only as
a kind of shorthand--terms such as "legitimate" to describe commonplace
practices such as scare quotes, thereby consigning emphatic quotation marks
to "illegitimacy."