The following code applies for when your comments are hidden by default.
If it is not your case, you'll have to simply add/remove some "jQuery('.commentlist').show();" and "jQuery('.discussion').show();". So please keep that in mind, I didn't test it for when your comment appears by default. You'll just have to test and change the code.
To make the "Toggle comments" link work in IE8, take this following code (in p2/inc/js.php):
jQuery("#togglecomments").click( function(){
jQuery('.discussion').toggle();
jQuery('.commentlist').toggle();
return false;
});
...and change it to...
jQuery("#togglecomments").click( function(){
var elem = jQuery('.commentlist:first');
if(elem.css('display') == 'none'){
jQuery('.commentlist').show();
}else{
jQuery('.commentlist').hide();
}
return false;
});
That's it for now. I learned JQuery as I was doing this, so it may not be perfect. But on my site, this made the comments toggle on both Firefox and IE8.