Depends on what he meant by "expert". If he meant he has PhD level expertise in D and that is his life's work, then it's completely understandable he wouldn't be happy doing Q, and would seek to do D elsewhere.
People tend to misuse words like "expert" and "fluent" though, when they're really not, but on HN odds are higher that they're using at least "expert" correctly.
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Depends on what he meant by "expert". If he meant he has PhD level expertise in D and that is his life's work, then it's completely understandable he wouldn't be happy doing Q, and would seek to do D elsewhere.
People tend to misuse words like "expert" and "fluent" though, when they're really not, but on HN odds are higher that they're using at least "expert" correctly.