Twinjo is a dual binary/text format that is supposed to be able to
encode a very wide range of data.

The current draft spec is very conservative:
https://github.com/johnwcowan/r7rs-work/blob/276681081f757dfac050771a8526fd0cbaae00e7/Twinjo.md

This is about in the ballpark of what POSE should aim for IMHO. The only
thing I would add is more escapes for strings and vertical-bar symbols
so that all Unicode codepoints can be represented.

The extended # syntax is appropriate for Twinjo. It's probably overkill
for POSE, though I'm willing to be convinced otherwise.

Bytevectors are a must for Twinjo, not sure about POSE. Opinions?