Ok, so there seems to be some terminology confusion here. I think there are at least two important issues to consider:
1) Which packages do we offer for installation for an admin. IMHO general-comments should not be offered even though it has user visible pages. It simply does not make sense stand-alone. Related to this is whether it makes sense for an admin to mount a package. Again, I don't think it ever makes sense for an admin to mount general-comments. Services tend to be auto-mounted and general-comments already auto-mounts.
2) Should a package show up as a link in user navigation (and as a tab in Lars's new subsite UI), i.e. does it have a user UI (as opposed to only an admin UI) that it makes sense for the user to navigate to? This may be the case for general-comments, although I'm not sure.
Both those two properties should I think be attributes of a package. My thinking was that apm_application would indicate 1). For 2) we would need a new attribute.
I think a full solution to this issue may be defered to after 5.0.