This just started happening to me today while doing a WQ in Val'Sharah. Every time an objective in the quest ticked (ie. killed a water sprite or "roused a druid of the fin") the quest complete effect would play and the chat log was repeating "[Carbonite] Quest Complete 'Talisman of the Shal'dorei'."
After leaving the group once the WQ was complete, I had this show up in the chat log (repeated about 4 or 5 times).
Code:
[Carbonite] LandMs 1
[Carbonite] LandMs 2
[Carbonite] LandMs 3
[Carbonite] LandMs 4
[Carbonite] LandMs 5
[Carbonite] LandMs 6
[Carbonite] LandMs 7
[Carbonite] LandMs 8
[Carbonite] LandMs 9
[Carbonite] LandMs 1
[Carbonite] LandMs 2