I have just updated my wordpress plugin called CommentLuv so that it uses AJAX and is able to work with users who are logged in (and not administrator of the blog).
Someone asked me in my forum if it was compatible with Mu, I think with the new changes I have made it is but I don't have Mu installed on my testing machine to find out.
Would anyone be willing to give it a quick test to see if it picks up "blog A"s last post on a comment made on "blogB" if they are logged in ?
it's a single php file that adds some javascript to the head of a single page which in turn, adds an image to below the comment form which changes to the users last blog post when they start typing a comment.
you can contact me on commentluv.com or fiddyp.co.uk