HTML validation problem in tslice?

Using the following rcfile:

<TREVERSE>
<SPAMMODE>
<MSGBODYEND>
$TSLICE(10;10;1)$
</MSGBODYEND>

I find that the thread slices doesn't validate - see
http://validator.w3.org/check?uri=http%3A%2F%2Funagi.mail-archive.com%3A8080%2Fproblem.html

Any suggestions? It looks like the problem is you aren't supposed to
stack <ul> tags. This occurs when the thread is longer than the
tslice.  It is not obvious to me what MHonArc resource can be modified
to make the HTML validate.

Cheers,
Jeff