>> I believe that a non-interoperable approach to keywords will inevitably
>> lead to the xkcd "standards" situation: <https://xkcd.com/927/>
>
> Seriously, what kind of interoperability is strived for on a technical level?

Though it is a joke, it's also a serious observation. The ten Scheme
implementations listed in the 177 rationale with their own native
keyword systems are not going to drop those systems if R7RS-large (or
177) specifies an incompatible system. Instead, they will add the new
system as an alternative to their existing one. That proliferation will
add more code and documentation to the implementation, and users' Scheme
code will have to choose which keyword system to use at the cost of
compatibility with the other one.

The precise amount interoperability achieved on a technical level is
everything in the Specification section of SRFI 177. Everything that can
be written using those tools (lambda/kw, define/kw, call/kw) is fully
interoperable with the native keyword systems of all Schemes listed in
the rationale.