(Isn't this actually a meta question? I would add the area51-meta tag.)
Downvoting here makes sense to me. Just as it does on the other sites.
The lack of an upvote just means there isn't active interest. A downvote means that somebody thinks it's actually unwarranted. Also, if there weren't downvotes to counteract upvotes, it would be difficult to get an overall "consensus" of the community.
But it's a good question. I'd be interested in hearing differing opinions.
From comments, it seems that the suggest improvements link should be used for commentary alongside the broader signalling of upvotes and downvotes.
Since answers should not be provided under suggested improvements, it should only be feedback on the quality or nature of the example question itself.
I would say that unlike the other sites where people who downvote like to remain anonymous, it might be more beneficial on this site to explain the reasoning—so that other people can see why some questions might not be useful. However, while such feedback is useful, I think that downvoting should always allow for anonymity—you shouldn't be expected to explain yourself unless you wish to do so.