"This is commentary on another post, not an answer."

Question

When prompted to recommend deletion of a given answer, the following pops up:

This is commentary on another post, not an answer

“This does not provide an answer to the question. To critique or request clarification from an author, leave a comment below their post.”

I find this very misleading. It seems like the bold phrase is unrelated (or at least poorly related) to its description. Why is this so?

EDIT: Based on some discussion on the comments, I'll further clarify my point:

What is it to be "commentary on another post"? Is the phrase intended to be "This SHOULD be a commentary?". I sincerely don't understand what the bold phrase is telling me. Not only that, but what is this "other post"? And even more, there are answers that do not provide an answer to the question and shouldn't be a commentary whatsoever.

For example, if someone asks to prove that $e_1,...,e_n$ are a basis for $\mathbb{R}^n$, and then someone answers: "This follows from the fact that every vector space has a basis"... this does not provide an answer to the question, is not "asjkadjklzxfjzkxc", and shouldn't be a commentary.

Answer 1

An important point to realize is that "not an answer" is to be taken in a formal way. The point there is mainly to correct misuses of the user-interface, comments posted as answers, new questions posted as answer, and maybe also to eliminate the occasional cat-on-the-keyboard post.

It is not to be taken to mean it does not resolve the problem in the question (as it is wrong, incomplete, etc.)

This is a recurring source of confusion and some proposals were made to change it, for example to "not an attempt to answer."

This addresses the "This follows from the fact that every vector space has a basis" example. It is not really in the purview of that queue to delete wrong answers, and there is thus no prefabricated reason for deleting it.

Now, to the bold phrase. The idea is in my understanding that the bold phrase is what you, the reviewer might think when reading an answer-post. Like "Wait, something is not right here. This post is not answering a questions. This is commentary on another post." When this happens then you chose this reason and in doing so you tell the author of the post via an automatic comment that: "This does not provide an answer to the question. To critique or request clarification from an author, leave a comment below their post." And "commentary" there should really mean the same as "critiquing or requesting clarification." If it is something else, do not use this reason.

This is the same for the other choices there. The bold text is some short-hand for common impressions one can have when reading an answer-post, sometimes using a bit SE-specific jargon, and the text below is the more detailed comment the author of the answer-post will receive when this reason is chosen.

Answer 2

Short version: This answer is for situations where users posted something as an answer that should have been posted as a comment instead.

So when is that the case? You as an experienced MSE user know that an answer (in the sense of solving the problem at least to a large extent, not in the sense of replying in a dialogue) should be posted as an answer. Everything else should be posted as a comment (except for things you should not post at all). That “everything else” can also be summed up as “commentary” or as “things like critique or request clarification”. So the bold text sums this up for you: if it's commentary as opposed to an answer, choose this.

The person whose post you're voting to close may not know as much as you about how SE works. They may assume that this is some kind of forum or chat, so that whenever they have something to say, they pick the big edit box, type in their text and click send. To such a person, saying “this is commentary, not an answer” doesn't convey enough meaning. Instead, the more verbose non-bold text tells the user
a) why posting this as an answer was incorrect and
b) what other approach would have been appropriate

Example of where this reason would have been appropriate:

Question: How do I prove that $e_1,\dots,e_n$ are a basis for $\mathbb R^n$?

“Answer”: Please clarify your notation: what is $e_i$?

Essentially, it is up to you to decide when this close reason is appropriate. Neither the bold nor the non-bold definition is a rule to follow blindly. Perhaps it would be better to change the bold text to “this should have been posted as a comment instead”.

If you think the post doesn't add value to the topic, even if degraded to a comment, then don't use this reason. I guess your “This follows from the fact that every vector space has a basis” could be seen to fall into that category, although it would be far from obvious without some understanding of the mathematical topic at hand.

Answer 3

The bold phrase expresses a potential classification of the item which, if true, is a valid reason for recommending its deletion.

That classification isn't necessarily true; that is your task as reviewer to evaluate.

If you choose that reason, then you assert that the classification is correct; you believe that the answer is commentary rather than a proper answer, and are recommending its deletion for that reason.

What the text should be is irrelevant; it is what it is and if it were something else, it would be a different text. This workflow is purely about deciding whether that object is to be deleted or not, not whether it can be salvaged by a transformation into another text.

If the answer has the form of a comment, but enough content to provide an answer (or combines commenting with answering), then it may be salvageable. You can edit the answer to improve it rather than recommending its deletion.

Deletion recommendations are for junk that can't be salvaged.

Answer 4

What is it to be "commentary on another post"? Is the phrase intended to be "This SHOULD be a commentary?"

Specifically on this point: the phrase is saying that it is commentary. That is to say (here I reach for the dictionary) it's "a series of comments, explanations or annotations". Being programmers, the Stack Exchange authors appear to have no problem with the notion of a series that contains exactly one value, because I don't think they mean this popup to exclude things that are exactly one comment, explanation, or annotation! They're using "commentary" as an uncountable noun.

Now, "a comment" also has a jargon-meaning relevant to Stack Exchange, of a particular kind of content that you add to the site using a certain part of the UI, and that's displayed in a certain way. This popup isn't saying that it's a comment in that jargon sense, it's saying it's commentary in the general English sense.

And so as it happens yes, it should have been posted as a comment if at all. They say "To critique or request clarification from an author, leave a comment below their post" in order to imply that not all commentary is suitable for posting at all. They're trying to guide users to use comments only for critique or requesting clarification, and not for explanation or annotation.

I agree that these messages are confusing, though. I doubt that it's uncommon for a rather puzzled user to be given instructions that don't relate to what they've done or the real reason for action, and perhaps that they actually cannot follow at their current rep. Hopefully the messages help most of the time. I'm not sure about this case specifically, but in the general area of closing/flagging/deleting there have been times where the reason for taking action has been gradually refined down to quite a focussed definition without necessarily changing the top-level name to fully reflect the new conditions. I generally don't bother close-voting questions any more (even on Stack Overflow, the site I have most rep on) because I don't really understand any more what several of the available reasons are supposed to mean. Sign of old age ;-)