@kudra @noam Friendica is also ActivityPub, just a different design than Mastodon/Calckey/etc. Those are all designed more toward "twitter-clone" layout and Friendica is more "facebook-clone" with the added layer of extensibility and compatibility (ie. server addons that add additional features, allow alternate ways of doing things, and even add support for connecting to other platforms like Tumblr).
"Filtering" isn't a protocol feature, it's just a server feature where it allows you to proactively hide the posts that match the filter.
In Friendica filtering is provided by an addon, the one mentioned by @petrescatraian is called NSFW (it originally only filtered NSFW and later got expanded to a simple configurable filter addon), there's also Advanced Content Filter (which is harder to use but offers more complex filters), and some specialty ones like the Language Filter (it tries to identify languages and hides posts when it's certain enough that you don't speak the language).
GNU social JP is a social network, courtesy of GNU social JP管理人. It runs on GNU social, version 2.0.2-dev, available under the GNU Affero General Public License.
All GNU social JP content and data are available under the Creative Commons Attribution 3.0 license.