I'm intentionally not reading your post, but the "it's old so I can spoil it" is never an acceptable stance in a world where they keep making more people. The world doesn't begin and end with your experience.

How can people ever discuss something in public fora if spoilers have to be eternally avoided? Keep in mind, people often disagree on what even crosses the line into being a spoiler.

People are allowed to discuss things they have experienced. If those people make a special allowance for others to catch up and experience something recently released, all the better.

Not spoiling something to others is a courtesy, not an obligation. People live by their own rules.

snape kills dumbledore