Something LJ lacks which I would value is a way to make a comment and mark it as "screened" or private from my end, so the originator of the thread can see it but no one else can.
Another frustration on LJ with "screened" is that I cannot make a screened comment and reply to it without unscreening.
Giving both owners and responders the ability to create some kind of privacy of discourse would be of value to me, and perhaps to others who are reticent to incite flaming, but wish to inform the owner of a perspective.