Wikimedia Bugzilla is closed!

See URL; for some strange reason, this markup:

<font color="black">
==Legend==
# Condenser coil (hot side heat exchanger)
# Expansion valve
# Evaporator coil (cold side heat exchanger)
# Compressor

produces this HTML output:

<p><font color="black"><a name="Legend" id="Legend"></a></font></p>
<h2><font color="black"><span class="mw-headline">Legend</span></font></h2>
<ol>
<li><font color="black">Condenser coil (hot side heat exchanger)</font></li>
<li style="list-style-type: none; list-style-image: none; list-style-position: outside;"></li>
<li><font color="black">Expansion valve</font></li>
<li><font color="black">Evaporator coil (cold side heat exchanger)</font></li>
<li><font color="black">Compressor</font></li>
</ol>

Note how the spurious font tag gets repeated in all the following paragraphs, headings and list items: I believe this is done by tidy, and is considered a feature.  However, also note the extra empty <li> with the funny style attribute in the output HTML.  The styling makes the extra list item effectively invisible, so that the only visible effect is that it messes up the numbering, making the list render like this:

   1. Condenser coil (hot side heat exchanger)
   3. Expansion valve
   4. Evaporator coil (cold side heat exchanger)
   5. Compressor

(Incidentally, when I cut and pasted the list here in Firefox, an empty "2." item did appear in the pasted output, even though none was visible on the origibal page.)

Now, can anyone explain what weird and wonderful interaction between the MediaWiki parser and tidy might be causing this?