We’re thinking more about this now that our API is nearing.
In the meantime, note that you can block any member from following you or posting comments on your content (look for the Flag icon on the member’s page).
At this time there are performance and cacheability impacts of blocking members everywhere that preclude us from doing this. In the future we would like to address this better.Skoolio commented
Private accounts are a must in this day and age Letterboxd is really behind the times in this respect