This addon is a plugin. You need to extract it to your /plugins folder to install it.
Reverses the sorting of comments so that the most recent one appears first. Also turns off the AutoOffset so people do not jump to the bottom of the page.
No guarantees on the functionality of this plugin - it's been a while since it was written. Messing with sort order can have all kinds of dire effects because of the way we load sets of data & html via ajax. But worth a shot!