First, a lot of people I know would never thank a machine regardless of how happy they are with the results. Second, a lot of people habitually say "thank you" regardless of their actual satisfaction level.
Because of these two things, I doubt that whether or not someone says "thank you" is a strong indicator of satisfaction or dissatisfaction.
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I'm skeptical of this on two counts...
First, a lot of people I know would never thank a machine regardless of how happy they are with the results. Second, a lot of people habitually say "thank you" regardless of their actual satisfaction level.
Because of these two things, I doubt that whether or not someone says "thank you" is a strong indicator of satisfaction or dissatisfaction.