Mixed feelings. I've had some additional information to add to a topic a few times, that I thought would be constructive to the discussion, but it was locked before I was able too. I could theoretically create my own topic in response, but that becomes messy and likely isn't warranted the majority of the time either.
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I agree with @Welsh. The person who should lock a topic is its creator, not the moderator.
The moderator should only close a topic if it has already achieved its main objective and is a source of spam.
This is a forum, and the goal is to be able to discuss topics, regardless of their timeline.
I understand that direct questions with straightforward answers may not add anything further. However, this doesn't mean that – without spam – the debate can't evolve into something more complex.
It should be noted that the moderator's job is not to close topics just because someone thinks the answer has been given.
I think there's far more junk scattered throughout the forum, like topics and posts with only one character, like ".", than should be deleted, rather than wasting time closing topics.