I have noticed that in some tribes, there will be comments that have blank avatars next to them, and where a username would normally be displayed, it says, 'unsubscribed'.

I was wondering, does this signify that a person who was once a member of that tribe, but has since decided to leave that tribe, is the cause of this, or is it that such people have asked to be removed from Tribe.net all together, and if this is the case, how is this done?