you can read that not as that Scheme prefix syntax alone is a big selling point, but the fact that it then supports Scheme macros (which are much better than in most other languages that support some kind of macros, partly due to the syntax making this easier).
Then you can read the rest of the sentence, for a bonus:
> and a compatibility library to run Pre-Scheme code in a Scheme interpreter.
Which means that you can do things like develop using this language within a normal Scheme development environment, possibly share code between developing for the PreScheme compiler target and non-PreScheme targets, etc.
> but the fact that it then supports Scheme macros
Good for them.
> possibly share code between developing for the PreScheme compiler target and non-PreScheme targets
"possibly" is a strong word, seeing that Pre-Scheme is a statically typed, explicitly memory managed subset and all. There's a very large and coarse-grained semantic leap.
> Scheme syntax, with full support for macros,
you can read that not as that Scheme prefix syntax alone is a big selling point, but the fact that it then supports Scheme macros (which are much better than in most other languages that support some kind of macros, partly due to the syntax making this easier).
Then you can read the rest of the sentence, for a bonus:
> and a compatibility library to run Pre-Scheme code in a Scheme interpreter.
Which means that you can do things like develop using this language within a normal Scheme development environment, possibly share code between developing for the PreScheme compiler target and non-PreScheme targets, etc.