This is very similar to /msg to [author] of the [node]. And here is why I generally support adding more private communication tools to PM: Public and private communication (or perhaps should I say personal, because I did not mean private in the sense of hiding something from the public, but rather in the sense of posting something that would be interesting only to particular users).

Additionally I think this is very close to the thinking I presented in (OT) Collaboration in Context as well.