> Maybe RMS, with his experience of AI research (iirc), > has a different view.

RMS primarily uses C and Lisp. Lisp source code is a tree already. And C is so simple you can get by with tags and such.

If he was a C++/Java/C# programmer (which he is not) he may have a different feeling on the importance of the AST relative to the risk of Microsoft using gcc with VisualStuio to offer advanced features while by-passing the GPL.