I swear this isnt for malicious reasons, I wanna do a sorta trial run of a story someone asked me to write without them seeing the same concepts used in this version. Is it possible to make a story or chapter public but make it unable to be viewed by a certain user?
I can see the technical problem that the stories are visible to people who aren't logged in, so even if a specific account is not allowed to read a chapter, they could still see it after logging out. So the system to achieve what you ask would require an account just to get to see the stories and then blocking one person. ...And that would be a rather heavy handed change to the existing system. If the main gist is that you want feedback on the chapter and possible rework done before revealing it to the main recipient, just ask around for people to be test readers and send the text to them. Then after feedback publish it normally.
I think test-readers are probably one of the most useful tools a creator can have, even outside of writing. Playtesting games is one of the most important parts, and outside input is only a bad thing in the case of trolls, troglodytes, and other such annoyances. Definitly the most viable solution to this little conundrum