The style sheet mechanism should definately not change the parse tree of the
SGML document. "Before text" and "After text" are okay, but elements should
not be introduced. If you want to put formatting within your text
transformations, you should create a new, non-HTML formatting language whose
parser is called only during the processing of the STYLE element.
This is, again, an issue of separating form and content. If the style sheet
can modify the parse tree, it will become impossible to validate the HTML
document without "testing it out" with every style sheet engine.
Paul Prescod