You're thinking about the AST as the-AST-for-LanguageX not the-AST-for-LanguageX-withAdvice. Including an AST node called `Region` or a decoration for "Region" that multiple AST nodes can point to (or vice-versa a list-of-region indicies pointing into the AST tree) _that is serialized and stored in the same kind of way that #region is for C# code_ would allow for multiple people to look at the code structured in the correct way while displaying that structure in different ways (color coding vs. block outlining vs. extra newlines vs ... you get the idea).