This is an ongoing problem with that moderator. But nowadays pointing that out prompts him to allege democracy (though with not all votes having equal weight) or personal abuse. And providing a number of specific, verifiable examples of his censorship is simply flagged as spam or offensive.
The mod not only should have refrained from unilaterally closing your question, but he should have paid attention to your improvement/edit instead of him being adamant about keeping it closed.
Even if his comment preceded(?) your edit, the rush to censor content --such as your question-- departs from the essence of moderation and from what he wrote back when he was pursuing mod privileges ("I am always open to the possibility that my understanding is wrong [...] I would err on the side of leaving questions open for the community to decide what to do.").
The mod had posted an answer to where he redirected you. There is nothing wrong with him redirecting the audience to a post he answered (it is natural for us to do that because we keep "fresher" in our mind the answers we ourselves author). The problem is that he coupled this with censoring your post, a decision which is disproportionate to the "harm" (if any) a duplicate question can cause.
Altogether what we see now is in contrast to the time when all [...] moderators explicitly committed to minimalist/laissez-faire moderation. But I'm glad to see that at least @RyanM's comment on this post as well as his vote to reopen your question drift from his recent stance that a moderator's "voice is worth more" than ours.