Main thing I can think of is an option for non-admin users to block an instance on the client side. Like blocking a community or user except it does both, for everybody from that instance.

Your options are pretty limited, then. This Wikipedia article has a list of all browser engines; if you want not obsolete and open source ones you’re looking at Netsurf or SerenityOS’s browser. That or one of the Firefox-derived ones (Pale Moon, etc).

Sorta not really related but Freya’s video on splines (“The Continuity of Splines”) is a virtually perfect resource if you’re interested in learning about… well… splines.