The site only allows you to see a certain number (10?) of levels of nesting at once. If the 'root' comment that you're trying to view grandparents of is nested that many levels in from the multi-great-grandparent you're looking at, you won't be able to go further up the thread. Changing the 'root' to the great-grandparent will allow you to go further up the thread, but the original comment won't be on the page any more when you do.
Given how that works, it's probably non-trivial to fix this - allowing arbitrary levels of nesting to show on one page probably breaks the layout. There may be workarounds, though...
In the next month, the administrators of Less Wrong are going to sit down with a professional designer to tweak the site design. But before they do, now is your chance to make suggestions that will guide their redesign efforts.
How can we improve the Less Wrong user experience? What features aren’t working? What features don’t exist? What would you change about the layout, templates, images, navigation, comment nesting, post/comment editing, side-bars, RSS feeds, color schemes, etc? Do you have specific CSS or HTML changes you'd make to improve load time, SEO, or other valuable metrics?
The rules for this thread are:
BUT DON’T JUMP TO THE COMMENTS JUST YET: Take a few minutes to collect your thoughts and write down your own ideas before reading others’ suggestions. Less contamination = more unique ideas + better feature coverage!
Thanks for your help!