I'm sure you considered whether optimizing for click-through rate at the expense of diversity of response "moods" (or whatever) was the right tradeoff. Why did you ultimately decide it was?
To be clearer on our metrics: In addition to qual there's also a precision/recall tradeoff, so saying ctr alone was an oversimplification. We have coverage targets, but that doesn't really impact the positivity of the suggestions.
https://www.youtube.com/watch?v=lLcpcytUnWU
The key line being: "I'm sure you believe everything you're saying, but what I'm saying is, if you believed something different you wouldn't be sitting where you're sitting."