Yes its possible but not in comment form unless you use a 3rd party tool.
You can either type the comment in the follow up field or edit the message
(or subject field).
The only tool I'm aware of that can do this is OutNote:
http://www.slipstick.com/redirect.asp?id=outnote
--
Diane Poremsky [MVP - Outlook]
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"Sarah Irving" <(E-Mail Removed)> wrote in message
news:56B13575-5348-4DA5-B603-(E-Mail Removed)...
> I would love to be able to add a comment (as in excel) to an opened
> received
> email which would detail the progress made realting to that email. Does
> anyone know if this is possible