I don't understand. Having those 3 quirky HTML tags is fine, but can users add other tags? How do they go about doing that? Can they enter the React definition

I don't understand. Having those 3 quirky HTML tags is fine, but can users add other tags? How do they go about doing that? Can they enter the React definition of those tags somewhere on their site's configuration? Or in the page? Or install them from a marketplace, like the Sticker Packs of some apps? Right now this reads as "content platforms today don't let you enter code, so publish with us we don't allow code but we have confetti".