klark0 - 10:37 pm on Nov 5, 2012 (gmt 0)

All posts are indexable (if the sharer allows the public to see it)

Hitting the +1 button on external pages, and adding a comment is also indexable on its unique URL (again ..if the sharer makes it public for all to see).

Even without making a comment, any url that is +1'd is added to the user profile's "plusones" tab (which is public and indexable by default, but can be made private by the user).