Tagging is available on any serious platform with lots of data. It can be used to search for or filter out posts to save time/energy.
Personally I skip about 95% of posts here -- a lot of that is based on the post's category.
Some e.g's of HN relevant tags (multiple could be used per post): Code, Software, AI, Crypto, Linux, Politics, History, Space, Math, Biology, Health, Robotics, Microsoft, Apple, Startup, Social Media, Study, Games, Entertainment, News
If readers don't want to use tags/filters they don't have to.