idna-mapping update

[John C Klensin]

--On Tuesday, December 22, 2009 01:20 +0000 Shawn Steele
<Shawn.Steele at microsoft.com> wrote:

>...
> The big difference seems to be the "why do we need these?"
> view vs. "what harm are they and they won't break stuff if we
> keep them in" view.

Shawn,

I almost agree with that categorization.  However, let me try a
different version in the hope of at least understanding each
other's positions better.

At least some of those you would probably characterize as of the
"why do we need these" view get there from a examining the "are
these harmful question" and getting to "can it be proven that
these are not harmful" as the key question rather than "what
harm are they", i.e., "you can't prove to my satisfaction that
they are harmful and therefore they should be treated as
harmless".

That difference is important, in turn, because, for some of us,
the more we look at font and stylistic variations -- much better
understood for some scripts than for others-- it begins to feel
as if any variation on, or alternate character for, a given
character carries risks with it, especially for users who are
not intimately familiar with a given script and the range of
artistic fonts and calligraphy that might be used with it.    If
the existence of some risk is taken as a given, then there is no
"harmless" and only a question about whether some particular
alternate character mapping has sufficient value to overcome the
risk.   And _that_, at least in my case, is what leads to the
position you characterize as "why do we need these".  Of course,
that position gets even stronger when we can see problems, as in
the superscript and ligature examples I discussed in my note to
Michel.

     john