According to https://en.wikipedia.org/wiki/Shadow_banning there is precedent from the 1980s, and Fogbugz had this feature in 2006. I don't know when Reddit implemented it, but by 2012 it was widely known that they did, so they may have implemented it first as well.
How was this patent granted?
See https://en.wikipedia.org/wiki/MUD and https://publishing.cdlib.org/ucpressebooks/view?docId=kt367n...
[MUD1] became the first Internet multiplayer online role-playing game in 1980, when the university connected its internal network to ARPANet.
Which dates that particular piece of prior art to 1980 or later.
She was made into an object if you investigated her. She was a "mirror".
Some discussion here: https://blog.codinghorror.com/suspension-ban-or-hellban/
Links to Metafilter discussion here: https://ask.metafilter.com/117775/What-was-the-first-website...
> On the Citadel BBSes I frequented in the late '80s, it was referred to as the "twit bit", and the disliked user would sometimes be said to have been "twitted".
We implemented it sometime in 2007.
I also seem to rember msn messenger also had a silent blocking feature. Your activity would be invisible to the blocked user and you'd appear as offline.
Ignoring a user is entirely client-side. You might be able to test it with a ctcp, depending how the client is designed and configured, and depending on their umodes (if ctcps are blocked) as ctcps are standard messages with a prefix.
Silencing is unlike Reddit shadow bans; firstly, it only applies to private messages, not to channels. Secondly, it has to be configured by the individual users, not by admins.