> Almost no implementation is without caveats with respect to RnRS support.
>
> Not having hygienic macros shouldn't be a requirement.  After all,
> there were several Scheme standards with no macros at all.
>
> Not having full TCO or call-with-current-continuation makes me
> nervous.  They've been part of Scheme since the beginning.  But as you
> say, such an implementation can still be perfectly useful.
>
> My only objection is when an implementation calls itself "Scheme"
> without prominently documenting such caveats.

Indeed.

Expecting implementation authors to document things in a consistent way
is not going to work - but consistency is one thing that Scheme.org can
ship!

IMHO the ideal approach would be a SRFI that specifies a metadata file
shipped in Scheme implementations' source release tarballs. We could
then download all the latest tarballs, read the metadata files, and use
that data to generate parts of the website.

The metadata could say (among other things) the names of OS packages;
what commands to run to build from source; etc.