Sometimes I really miss Jaiku. There you could add multiple streams to your feed, but when following, could also decide to follow certain streams, or not. So I could follow someone's post, but not their flickr pics or delicious bookmarks. Comments on a post where separate from posts as well. Twitter makes this all one big mess.
Let's hope annotations will be used to add this filtering (although I haven't seen post client, which is an annotation as well, used for this).
That's about what I envisioned while reading the article. All you'd need is different sections on Twitter, and to choose which to subscribe to when following someone. All the clients would need to know is that you're subscribed to X's stream 0 but not their stream 1.
