I'm making a modernized BNF-style metalanguage that supports grammars for text and binary formats, but unless there's some kind of outside review, I won't find any blind spots I have until long after release.

If you have experience in grammars or protocols (text or binary), could you take a quick look?

Note: I'm not aiming for perfect expressivity; just 80-90% of use cases without making things overcomplicated so that it can be used descriptively in documentation.

https://github.com/kstenerud/kbnf/blob/master/kbnf.md

Some examples of it in use:

* Internet Prodocol, version 4: https://github.com/kstenerud/kbnf/blob/master/ipv4.kbnf

* Concise Text Encoding: https://github.com/kstenerud/concise-encoding/blob/master/cte.kbnf

* Concise Binary Encoding: https://github.com/kstenerud/concise-encoding/blob/master/cbe.kbnf

* The KBNF grammar itself: https://github.com/kstenerud/kbnf/blob/master/kbnf.md#the-kbnf-grammar-in-kbnf