Avatarring and Feathering is considered to be a tongue-in-cheek punishment, as it is not significantly destructive to the user's online experience (in contrast with banning / kicking.) As such, it is levied upon extremely minor offenders, or even as an in-joke for some specific contextual purpose within a thread.
The application of Avatarring and Feathering serves a purpose more similar to that of the dunce cap or the scarlet letter in earlier times. By comparison, the real-world punishment of tarring and feathering often caused moderate-to-severe injuries to the victim as the hot (sometimes boiling) tar was poured onto the skin.
The first known utterance of the phrase occurred on 5 May, 2013, when a user, posting on a sportscar-related web forum, had his avatar changed from that of an automobile on fire to one of a stylized pink pony character from the popular television show "My Little Pony: Friendship is Magic." This was done after he employed the word Brony in an apparently serious context while responding to another user, whom he suspected of trolling.
"Can we please avatar and feather ^that guy^?"
"Great, I've been avatared and feathered. Can a mod please change my avatar back to something OTHER than a pink pony now?"