All,
This is probably well known to most of you, but the General Category Value in the Unicode Character Database and the stability of that value are not very relevant to IDNA, which does not depend on the Unicode Categories.
IDNA depends on the Unicode Normalization Form KC table, and there have been very few changes indeed in this table:
http://www.unicode.org/Public/UNIDATA/NormalizationCorrections.txt
Also, IDNA apps depend on tables for converting from various non-Unicode encodings to Unicode. This is another place where instability could affect lookups, potentially even in dangerous ways. Stringprep and IDNA already mention this issue in their Security Considerations sections.
Erik
