I think I figured out how to stop the obnoxious notification spam that has been telling me “[name] mentioned you” every time somebody reblogs a post I was ever tagged in, even if they never mention me in THEIR reblog!
1. Go to Account, the little person head and shoulders in upper right.
2. Go to Settings, with the gear icon.
3. Uncheck the new “conversational notifications” switch.
It’s not there for me (maybe they enabled it before making it an official thing in my country?) but hopefully my followers will be able to turn it off!