In the template MTDoubleSlide, the comments should have a small icon at the top left corner called expandall.png.
This is not showing.

Go to the file:
YOURSITE/components/com_comment/joscomment/templates/MTDoubleSlide
-and download the file called index.html
Open it in some editor.
On line 134, you will see that the image source direction is lacking a preceding backslash.
So it should look like this:
/components/com_comment/joscomment/templates/MTDoubleSlide/images/expandall.png
then save the file, and upload it. Fixed.
Now that took me about 3 days to figure out...

This is not really visible in Firefox etc, as FF closes tags etc automatically.
But this looks a bit bad in IE, as IE doesn't handle this, and just leaves a blank image placement. Which of course looks a bit.... :lol: