Processing titles for the PDF TOC

Hi all,

I'm using docbook-xsl-1.73.2 and Saxon 9 HE to generate PDFs via XEP.

I'm attempting to strip any "remark" elements that authors have embedded
in "title" elements from the content reproduced in the TOC. As far as I
can tell, simply adding 

    <xsl:template match="remark" mode="titleabbrev.markup"/>

should have done the trick, but it hasn't. In fact, none of  

    <xsl:template match="remark" mode="label.markup"/>
    <xsl:template match="remark" mode="toc"/>

has made any kind of impression, which is puzzling. 

From what I can see, the processing for the titles found in the TOC is
done via the toc.line template, which generates the title content via
<xsl:apply-templates select="." mode="titleabbrev.markup"/>, so
<xsl:template match="remark" mode="titleabbrev.markup"/> should prevent
remarks from being processed. I can see nothing in the scripts to
override it, yet the continuing presence of the remark elements in my
output says otherwise.

Suggestions?
Jeff.