Unfortunately if you are sending the friend list as part of the cached page then you won't be able to use that cached page for all users.
I believe the original comment was that each comments page should be cached globally and then each user can have their friend list & dynamic data fetched separately and added to the page using javascript.
Ah, my bad then. I don't think the comments pages cache well though--the votes are always going up and down. My understanding that in addition to pulling all the comments for each request they were also pulling the friend relationships for the current user with all the participants.
The page would be regenerated on each new comment, of course.
Votes should be done the same way friends' lists are: on the client side, via javascript. The cached page with its comments would include Javascript to grab the most current scores for all its posts (one request) and modify the DOM appropriately.
I believe the original comment was that each comments page should be cached globally and then each user can have their friend list & dynamic data fetched separately and added to the page using javascript.