agenda+ Which definition of whitespace to use?

Specdev currently has 
https://deploy-preview-77--bp-i18n-specdev.netlify.app/#char_whitespace

But this recommends 3 approaches, only 2 of which make it to the 
mustard, and it's still not clear to me which to use when.

Other questions include:
- do we really want to recommend the use of Z property, especially given 
that it doesn't include obvious ASCII whitespace characters? Where did 
this recommendation come from?
- why are RLM and LRM included as whitespace in some definitions, but 
not RLI, LRI, PDI, etc.?


It would be great if we could discuss this tomorrow.

ri