I’ve heard quite a few people unhappy that the new achievement system spams their guildchat relentlessly, even when they’ve turned off global achievement announcements.
Here’s how to disable them:
For nearby/chat announcements
Right click on the tab of your chat window
Go to “Settings”
In the left-hand column, pick “Other”
In the right-hand area, look for an option for ‘Achievement Announce’; [...]