Stuff that makes sense for who has js and does needs to be available to whom does not have js:
Posting, editing posts, moderate a post (lock, move, etc...), read posts, navigate to all pages the normal user that uses js can, hovering & appear (CSS ).
Stuff that makes sense for who has js and does not need to be available to whom does not have js:
Quick (insert-name-here (reply, edit,...)), anything dynamic that is not hovering & appear (I.e cannot be made using CSS only), multiquote, infinite scrolling, basically anything else you can think of.
BTW, are you calling idiot to 2,213,329 firefox users?!?!?