The achievement isn't simply unlocked by reading the letters, there is an additional requirement.
On a new character, the letters are already torn while on a character that has completed living world season 3 content can unlock the achievement. I'm not sure what the exact condition for unlocking is. —The preceding unsigned comment was added by 184.108.40.206 (talk) at 22:16, 6 September 2017 (UTC).
- Thanks for that extra tidbit. In time, we may get this narrowed down further. G R E E N E R 18:20, 18 September 2017 (UTC)