Re: UAX #9: applicability of higher-level protocols to bidi plaintext

My claim is that in the absence of an agreed
or conveyed higher-level protocol, this default must be respected.

Not how higher-level protocols work in Unicode.

If you say that you support the default, then you better support the default but if you say otherwise, you can single-handedly declare a higher level protocol (or effectively declare one) and then be conformant if your HLP modifies otherwise modifiable (tailorable) behavior.

There's no concept here of "sender and receiver" or means of expressing binding agreements between them.

Not just for UBA, but all similar cases in Unicode.

Now, you can create a protocol that makes such guarantees, like W3C does for HTML/CSS where some style values do mean "follow the default" for  a given paragraph and you would not be conformant to either Unicode or the W3C specs if you didn't do that.

A./