Or is there a way to disable it? There are a couple others but that particular one I see constantly.
The argument in the URL is annoying because it causes duplicate / different URLs in the eyes of Google plus.
What this means is that a page can get +4 at the root url and +2 by people who found the page via the activity feed but the SEO benefits don't stack to a single page.
I'm sure it had some legacy tracking for ning but I am constantly having to remove it when working on the site.
I agree. Though it is funny seeing it in the nav bar above your discussion.
While we're at it, we can also drop the ones in email notifications & newsletters for the same reason
I agree +1