Hi Wyndham,
I think if you remove the hard linebreak between the red words "creating" and "or editing" then Calibre will read the Comments OK. At least it worked for me.
I'm afraid I can't help with the Cover question, but you could always resort to dragging the image onto the Calibre Edit Metadata screen.
Code:
<META NAME="COMMENTS" CONTENT="<P>This document is used to set the coding to be used when creating
or editing HTML source documents, prior to importing into Calibre.</P>">