BuddyPress.org

It would be really good to see some sort of integrated video commenting – I believe that, for certain use cases, video commenting could be extremely useful but, so far, it has been hampered by clueless implementations (Seesmic, Viddler) which forced users to jump through registration hoops before they can actually record their message, killing the medium before it even had a chance to catch on.

As far as I can see, Kaltura does not currently offer any sort of video commenting but I think it would be a really could fit with the way in which you are trying to push the communal aspects of video.