Is there, anywhere, a definitive guide to how micro.blog truncates posts it receives via RSS?

Strange question, I know, but ... Is there any way I can restrict access to a post in WP without having to make people jump through **any** hoops to see it?

There are lots of solutions that allow only registered users to see a specific post. What I want ideally is a link I can give people that will work for them and not for anyone else. A page hidden from anyone who does not have that link.

The idea is to give email subscribers and other supporters access either exclusively or well in advance of the general public.

Just read a horrible coinage: autonomobile. Cars were never automobile without a driver. We are still waiting for a truly automobile means of transport.