Guy 1: When he first got diagnosed six months ago we were told that the prognosis was encouraging.
Guy 2: So when did the doctor let you know that it wasn't looking / didn't look quite as encouraging anymore?
What tense should I use here? Are both options possible? The simple past "didn't look" sounds more natural to me, but can't back it up.
Both are equally idiomatic, partly because the present tense versions of both are equally used. The doctor might say either "It's looking encouraging" or "It looks encouraging," because this use of "look," to evaluate current conditions, is often used in the continuous tense without necessarily implying an ongoing process.
You wouldn't get the same result with other verbs. "I'm stopping" and "I've stopped" are different. "When did the doctor let you know he was stopping treatment" and "... he had stopped treatment" would have different meanings.
