That is facinating whilst also being awful.

I trained in Scots Law. We (Scotland) used covenants in fuedal property titles for things like building specifications (roofs must be made of X slate, walls of Lothian greenstone) or restrictions on trades (no tanneries or breweries) or immmoral purposes (no selling alcohol). These were often sneakily designed to benefit the seller of the land by obliging the buyer to build their house out of materials from the sellers quarry. I don't remember seeing any use of them to restrict who could live there on "social" grounds. I wonder if it happened. I'll ask around my mates who still practice.