I'm actually glad to hear you're studying Tumblr and its ilk. There are a lot of things I like about Tumblr but the lack of comments and the resulting need to wade through reblogs in reverse chronological order to find - if you're lucky - the post everyone is replying to drives me mad. (I've seen people roleplaying on Tumblr and I simply have no idea how they can stand it.) I'd love to have more of the simple-upload-post functionality of Tumblr that retains the actual-working-comment-system of DW and does it intelligently.