Youtube was blocking comments mentioning Fediverse and ActivityPub 2 years ago way before all the exposure the Fediverse got last year. Facebook was blocking links to mastodon instances also before all that. There is absolutely no way a very specific word such as Pixelfed would be blocked "accidentally", how do you propose such accidental block would even be possible? Oops, intern smashed his butt against a keyboard and set a filter that happened to catch Pixelfed by accident? Come on.