> I have several lists configured with a BOTTOM_BANNER thusly:
>  <mailto:listserv&body=unsubscribe%20comp_incisive>
>
> When the user clicks on this, what shows up in the email form is
> To:  listserv&body=unsubscribe comp_incisive

If this is in the BOTTOM_BANNER template, you're a bit at the mercy of the
user's email client, because this is pseudo-HTML syntax appearing in
plaintext.

> Any known work arounds?

Most email clients will recognize a bare email address, and users of the
ones that don't will be used to handling them. This doesn't get you the
body=etc parameter, but you could use the RFC 2369 generic unsubscribe
address format:
   [log in to unmask]
assuming your version of LISTSERV supports it.

Hal Keen