My point still holds, just replace manipulating the structure of a program with manipulating the structure of a grammar. In no way is that comparable to manipulating raw parse trees.
Furthermore, when adding syntax you are not limited to a Lisp-style grammar.
You aren't limited to Lisp-style grammar in Lisp either. You can write reader macros if you have to. The point is, that on a basic level manipulating s-expressions is far easier to think about than manipulating the syntax of whatever the flavor of the day language is. You're essentially trying to invent reasons why macros in other languages are the same as Lisp macros and it's simply not true.
Lisp macros manipulate Lisp code once it has been read (parsed and tokenized into lists) and sometime before it is executed. That has nothing to do with grammars. Common Lisp also offers a facility to augment or replace the parsing and tokenizing mechanism in an unrestricted fashion.
