I couldn't make it work. Added it to the browser toolbar, clicked on it, refreshed page. No joy.

works great!
puts related videos below the player and comments on the right.

The only decent add-on to get comments on the side. Still buggy though, if I set always on youtube the comment section becomes blank with only way to fix is to reinstall the addon. Works perfectly if Only when Click is set.
Hope You could get it fixed and Thanks for porting it there.