I see two problems with his "volume" solution. The examples given show a fundamental divide: there's the song you've spent years working on, and then there's some random comment someone felt the need to get off their chest. There's one problem with the volume metaphor. How often would people change the volume? What's a mid-volume update, or an update with the volume set to 75%? The second, much bigger problem, is that using "volume" is a confusing interaction; people are already used to using those volume slider controls on websites to control the volume of sounds. The UI is telling them one thing, but the functionality isn't consistent with the typical website experience.
Offhand, I'd say maybe create a separate category called "Announcements" to take advantage of existing psychology and etiquette. Who would "announce" something like "mmmm... Cheetos." or "gonna get my drink on 2 nite!"? Maybe they'd get called "announcement whores".