So I took a quick peek and couldn't see this posted anywhere, mods feel free to delete if it has been. This was brought up in my game the other week in a post and it's too damn good not to share.
Basically there's two quick, painless steps to make this happen but once you have you will wonder how you ever managed to live without. Firefox is required.
Greasemonkey is required for the next spiffy little thing. This guy is also super easy to install just hit add to firefox and once it's installed it will prompt you to restart. Say hi to the little monkey in the corner (for the next thing to work the monkey must be in colour, which can be done by clicking on it)
Thread unfolder. Again pretty basic set up to add it to your firefox. What'll happen is in threads that get collapsed beside post new comment (as long as the monkey is in colour) you'll see unfold all and it will unfold the entire thread.