The add-on is a single script:
/run WorldFrame:HookScript("OnUpdate",function()SetCVar("Outline",0)end)
you could paste it in the chat box and it would work but you'd have to do it every time you log in. This way it automatically runs without you having to do anything. As you can see in the image below the questgiver has neither an annoying yellow outline nor the equally as annoying sparkles.
