> The Gambit in the browser site is at Gambit v4.7.0 and hasn’t been updated in a long time.  That’s why I’m looking into rebuilding it with the latest Gambit and emscripten (and compressing the generated JS/wasm code).

OK, that explains. You should verify that syntax-rules conforms to the
R7RS spec though: it has some extensions on top of R5RS syntax-rules.
For example:

(define-syntax foo (syntax-rules () ((_ first ignored ... last) (list
first last))))

(foo 1 2 3 4 5) => (1 5)

> I’m not sure I’ll have time, but it would be nice to add an in-browser code editor to create files (rather useful to try out writing libraries).  I may reuse parts of my codeBoot project which is a in-browser IDE for JavaScript and Python.

If we can get people collaborating on try.scheme.org, we could add one
code editor there that works with all the supported JavaScript Schemes.
In the best case, it could save everyone some time finding and fixing
bugs with the JS libraries <-> Scheme integration and end up with a
result that could be re-used on implementations' own websites as well.

I'm happy to supply Linux SSH accounts to people who want to experiment
with improving the scheme.org community subdomains, and as always, each
Scheme implementation is also entitled to have its own subdomain and
nested subdomains.