For code review, and general technical discussions, we are loving and using alot the ability to comment on code on the bitbucket site for each commit..
However if the commit it large, its hard because you have to page through many pages to see if there is any discussion, or chat. it would be nice to at the top have a list of such comments , and be able to click to go directly to it in the page..
Also in a busy system, it would be nice to search, and filter by commits that have these discussions..
plus for an individual file it would be nice to see all discussions regarding that file over its history, and not just this particular commit (a bit like some BLAME stuff)