.plexignore files are handy, but far too limited, as they apply to all libraries. I would like the ability to define separate rules and filters for individual libraries. This could be added into .plexignore or simply as part of a library settings - blacklisted (or whitelisted!) terms, file extensions, etc.
No, they apply to folders.
Surely you haven’t added the same folder to several libraries. Or did you?
And if I did? That’s how my library works: all of my movies happen to be tie-ins to an existing TV show.