During compile-time, it doesn't care. So you can use "illegal" characters for the names of macros.

  (macro what? (function () (return '(a b c))))
  (what?)

That compiles just fine to the JavaScript code

  a(b, c);

It does try to validate identifier names during code generation though (using the esvalid module), so if you give it

  (? 1 2)

then it will error with

  [Error] Identifier `name` member must be a valid IdentifierName
  At line 1, offset 1:

  (? 1 2)

(In a terminal, the offending character is highlighted.)