You can add XSL comment tags to a document, or you can wrap a selection in XSL comment tags.
Add XSL comment tags to a document
Do one of the following:In Design view, select Insert > XSLT Objects > XSL Comment, type the contents of the comment (or leave the box blank), and click OK.
In Code view, select Insert > XSLT Objects > XSL Comment.
You can also click on the XSL Comment
icon in the XSLT category of the Insert bar.
Wrap a selection in XSL comment tags