There appear to be a relatively small number of issues
still remaining in IDNA2008. Here's my shot at identifying them. They are
stated as "consensus requests", but need more discussion before we'd put them out as such.
Strongly discourage any local mapping except for a generic mapping aimed at providing compability with 2003, to prevent interoperability and security problems. Encourage use of the generic compatibility mapping to provide for a smooth transition.
For example, for #5, if it is because of visual confusability with URI/IRI syntax characters, then we should say so and give the paradigm example (FRACTION SLASH). This does not request a change in the protocol, but just an avoidance of unsubstantiated claims.
A-Labels be checked for validity when doing lookups?
Once a label is valid, it remains valid under any future version of IDNA, including changes in the registry (CONTEXT). In particular:
Invalid labels are clearly not stable, in that an invalid label may become valid in later versions of IDNA, or because of IANA registry updates: