Right now we can chose to be notified when a user creates a new post on his profile stream. Sadly this doesn't apply to new community posts, if the user chose to show those on his profile stream.
This is why I'd like to have the additional option to be notified when there's a new community post on a users profile stream. Of course only if the user chose to show community posts on his stream.
One could argue that I should join the community the user is posting to. But maybe I'm not at all interested in joining this community but I don't want to miss this users posts either.
This is why I think this additional option might be of use and could enrich the interaction between users.