First, he takes (∞,1)-categories to be categories enriched in spaces.
Then he takes categories enriched in spaces to be categories enriched in spaces!
I think that tautologies are off topic. Had he posed the question differently (i.e. used a different model of ∞-groupoids), then it might have made sense, but he didn't. Which reminds me of the fatuous "proof" of the homotopy hypothesis:
Define an ∞-groupoid to be a kan complex. Define a space to be a kan complex. Therefore spaces are the same thing as ∞-groupoids.
]]>Edit: I've given up because it is a pain in the neck to search meta.
Anyway, the answer that was given last time was that only the person casting the final vote to close should leave a comment (this is what I remember. I think that other people will remember this as well).
]]>Yeah, the last person who votes to close is really the only one who matters anyway, since that is the person who leaves a comment.
Please do not think like this! It's poison! If you vote to close, you should be doing so for a good reason, and you should do your best to articulate it. I know that the list of reasons for closing isn't very good, and I don't expect people to waste a lot of time worrying about which bad-fit reason to pick. Just pick one, but leave a comment with the real reason!
I regard voting to close without leaving a comment (or voting up a comment) as far worse etiquette than downvoting without leaving a comment. In the vote-to-close situation, the main argument for not commenting when downvoting (desire to preserve anonymity) is removed: when the question is closed, your name will show up on the list of people who closed it. The only reason I can think of for not leaving a comment when voting to close is that you can't come up with a way to do it without being a jerk, and in that case you likely don't have a very good reason for voting to close.
]]>On the other hand, I agree with fpqc and Andrew that the list of reasons to close is wholly inadequate. If we could design our own list, suitable for MO, that would be much better.
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