Simples! The image is on Flickr, the Flickr page it's embedded in allows comments, so embed the Flickr page in the blog and away we go.
Except that there's no way to embed a Flickr page in another blog, other than a rather clumsy iframe. And commenting on Flickr requires registration and log in, so there's not likely to be a free flow of comments. And if people do make comments, how do I solve the problem of divided attention between sites (which occurred when I tried FriendFeed embedding recently).
So maybe a better way is:
Please use the comments below to discuss what you can tell about this virus from the diagram.