On Chem.SE, whenever I close a question without explaining myself, Community♦ flags it (something like "question closed without comment").
I recently closed this question on Physics (I reopened it later, the close was a mistake--I meant to close something else). Community♦ didn't flag anything, even though the post had zero comments.
I feel that it should be the other way around. It is much more important for Community♦ to flag on graduated sites than on beta sites (though having the feature on both would be good as well). On a beta site, it is generally a moderator closing the question (who should know that a comment must be left). Even if it isn't, the volume of closed questions is low, and it's not too hard for mods to look through
/tools (or use a
closed:1 search) and review the community-closed posts.
On the other hand, on graduated sites, mods are not always present for each close, and it's harder to review community-closed posts. A post closed without a comment is thus something that is much harder to catch. And yes, it does need to be caught--some closed posts are salvageable, and need a "Do X, and we may reopen it" type comment. Others need the reason behind closing to be explained to the OP so s/he won't make the same mistake again or be scared off from the site.
Could we have the feature on graduated sites, please? (Maybe excluding SOFU sites which have too many flags already)