Sure, but it is not Mathematica's InputForm:
https://reference.wolfram.com/language/ref/InputForm.html
The majority of code is written not in FullForm. In Lisp 100% of the code is written in s-expressions.
> Clisp is not the only lisp - I can name 10 others that cannot be compiled.
Typical Lisp and Lisp dialects all can be compiled: Common Lisp, Emacs Lisp, ISLisp, Scheme, Racket, ...
Which Lisps can not be compiled?
Do you really know what you're talking about here?
https://docs.racket-lang.org/raco/make.html
>The raco make command accept filenames for Racket modules to be compiled to bytecode format.
That's not a compiler...
I don't claim to be an expert on lisp, so further googling I find
https://racket.discourse.group/t/chez-for-architectures-with...
which has some discussion about this and that native backend.
Suffice it to say I am not any more confident that being compilable is somehow intrinsic to lisp.
https://docs.racket-lang.org/reference/compiler.html
"18.7.1.2 CS Compilation Modes
The CS implementation of Racket supports several compilation modes: machine code, machine-independent, interpreted, and JIT. Machine code is the primary mode, and the machine-independent mode is the same as for BC."
CS is the new implementation of Racket on top of the Chez Scheme runtime. Chez Scheme is known for its excellent machine code compiler.
"Machine code is the primary mode"
> Do you really know what you're talking about here?
Read above.
How can I make this any more clear? You are able, in Mathematica, to write Plus[a, b] with your own fingers on your own keyboard and it will be interpreted as the same thing as a+b
> I'd expect that they can.
Clisp is not the only lisp - I can name 10 others that cannot be compiled.