I was thinking that applications like operating systems reveal the language they are written in as they are extended and there is too much c++ in texmacs to port it over to emacs which appears to be written in c. I can’t really comment on guile without researching it but the low level ideas are between scheme and lisp are incompatible with the lisp language, and I think he mentioned that when he said ‘non-Lispy language would be a mistake’.

Mostly because the huge gains in speed that were desired were found in the native compilation fork.

That, and the R5/R6/R7 debacle has alienated many from scheme.