This meta question is actually mostly answered in PSA: When reviewing, don't post duplicate (and near-duplicate) comments! But since this question is narrower and has a different focus, and it may not be immediately obvious to some how that one applies here, I've written this answer to address the specifics.
Just like any answer that contains insufficient explanation, a command-only answer:
- sometimes warrants removal as very low quality,
- occasionally can be improved significantly even by a small edit,
- sometimes should be kept, even if it can't/shouldn't be edited by reviewers.
Whether or not an answer should be considered so low quality as to warrant removal depends on the specifics of that answer, and on the context. Does it provide value? Even actual link-only answers are not always removed.
In any case, the main problem with link-only answers does not apply to command-only answers. Command-only answers do not become meaningless due to some other resource besides Ask Ubuntu changing or going offline.
So of course you should not use a comment about link-only answers on an answer that doesn't even contain a link--that doesn't make any sense.
But there's a bigger matter at play here.
You might be using the review system incorrectly.
The wording of this meta question strongly suggests you might be thinking you're doing one sort of thing while reviewing, when actually you're doing something entirely different.
I just flagged that one as link-only answer on the Low Quality Posts
It seemed the best matching category at least.
You appear to be under the impression that the Add a comment for the author? selections (where you can pick a comment when voting to delete posts in the Low Quality review) are a form of flagging.
They are not. When you use select a comment there, you are not flagging the post. The sole purpose of selecting something other than the default "No comment needed" option on that screen is to post comments that the author and others will see.
When you actually click the "Recommend Deletion" or "Delete" button, you are doing something similar to flagging. But the result of clicking this button that is not in any way altered or customized by whether or not you selected a canned comment from the list above it, nor by which one you selected if you did.
Please see PSA: When reviewing, don't post duplicate (and near-duplicate) comments! That explains:
What is and is not happening when you select comments in the "Add a comment for the author?" dialog.
What to do when there's something wrong with the post but none of the precanned comments offered there capture the problem. (The short of it is: select "No comment needed" and, if you believe a comment is warranted, post your own.) Really, that situation is what this meta question is about.
- Command-only answers are usually not very good but they are not the same as link-only answers.
- The precanned comments offered by the "Add a comment for the author?" dialog when deleting posts in the Low Quality review are not a form of flagging. The comments you leave through that dialog have no special effect or importance compared to commenting manually.
- If you've been selecting comments on that dialog based on the belief that you've been flagging or categorizing posts for the system, and if in doing so you've been posting comments that don't make sense or that otherwise are things you would not want to say... then you should stop doing that.
- If no comment offered under "Add a comment for the author?" is correct for the situation, stick with the default "No comment needed" option.
- If you believe a comment is needed, but none of the comments offered under "Add a comment for the author?" are correct, you can stick with the default "No comment needed" option but comment on the post manually yourself.