Don't know what's possible to do with the existing blog server-side script, but in the meantime here are two javascripts!
This one reverses only the numbering of the content:
CODE
<ol id="reverse_numbering">
<li>foo</li>
<li>bar</li>
<li>baz</li>
</ol>
<script type="text/javascript">
var reverse=document.getElementById('reverse_numbering');
reverse.style.listStyle='none';
var li=reverse.getElementsByTagName('li');
for(var i=0; i<li.length; i++)
{
li[i].insertBefore(document.createTextNode(li.length-i+'. '), li[i].firstChild);
}
</script>
This one reverses both the content's order and numbering:
CODE
<ol id="reverse_all">
<li>foo</li>
<li>bar</li>
<li>baz</li>
</ol>
<script type="text/javascript">
var reverse=document.getElementById('reverse_all');
reverse.style.listStyle='none';
var li=reverse.getElementsByTagName('li');
for(var i=0; i<li.length; i++)
{
li[i].insertBefore(document.createTextNode(i+1+'. '), li[i].firstChild);
reverse.insertBefore(li[i], reverse.firstChild);
}
</script>
Note that if a browser doesn't support javascript the original order will appear.
And if a browser supports javascript but doesn't remove the list-style (unlikely but possible in e.g. Opera with an user style sheet), you'll get something ugly like
1. 3. baz
2. 2. bar
3. 1. foo
To minimize such calamities it might be better to start with an unordered HTML list.