Unfollow is the opposite action of following someone, typically on a silo, commonly implemented on asymmetric follow silos such as Instagram, Google+, initially pioneered by delicious, Flickr, and Upcoming, but most greatly popularized by Twitter in contrast to the mutual friending model from explicitly "social" silos from Friendster to Facebook.
u-unfollow-of post. This would require comparing dates of the follow and unfollow posts to be sure what the current state should be. Especially difficult if someone follows and unfollows multiple times, since webmentions of any of those posts could be resent at any time, so the receiver has to look through all of the follow/unfollow posts it's received from that follower. 410 delete of the original follow post seems clearer, more explicit, and much easier to handle for receivers.
There are no known indieweb examples of an "unfollow" feature.
Examples of silos that implement an "unfollow" feature in their user interface, along with some differences.
- Instagram - upon unfollowing someone, refreshing your reader view removes posts from that someone
- Google+ - If you remove someone from circles i.e. unfollow them, then the previous post you received also disappear from timeline.
- Facebook - started as a symmetric friending model only, later added ability to only "follow" people rather than "add friend" (request friendship)
- You can also "unfollow" a post, that is, stop receiving notifications for it which you may have been automatically receiving because you wrote the post, you were tagged in it, or you RSVPd to it, etc.
- Twitter - upon unfollowing someone, you won't see future posts from them, but their past posts will still show up in your reader (home page) view
- emergent behavior: people post "@-name unfollow" posts when they are either annoyed with someone and threatening to unfollow, or do so sarcastically/ironically in response to some humorous thread. In neither case do they actually unfollow the person. So in practice there are "unfollow" posts that aren't actual unfollows.
- See Tweets with "unfollow"