Low quality is not the same thing as wrong, incomplete, or unreliable. An answer that is readable and apparently addresses the question passes the quality test.¹ When an answer: (i) fails the test; (ii) is impossible to fix or would take an unreasonable amount of effort to fix; and (iii) does not fall into another low quality category (spam, abusive, or not an answer), then it is appropriate to raise the Very Low Quality flag.
Consider that a Very Low Quality flag is a flag for deletion. But a wrong or unreliable answer is still valuable to readers because it attracts downvotes. A downvoted answer warns a reader “don’t go this way”. A deleted answer does not have the opportunity to warn readers of anything. Also, moderators have been told we are not arbitrators of whether an answer is wrong. That decision is left to the whole community by way of up- and downvotes. Deletion is for answers on which a downvote would be wasted: answers that are not even wrong.²
Moderators have been told to be sure the reviewer’s chosen flag strictly applies to the post. “The system has to be able to trust the accuracy of quality related flags”.³ There are actions taken behind the scenes which are different for different flags. These depend on accurate flags. Past flags are also used to train reviewers through review audits (not currently active on our site, but has been in the past and probably will be again). The review audit system also depends on accurate past flags.
In short, if the answer is right or wrong, reliable or unreliable, vote it up or down. Otherwise, if unsalvageable, flag it.
Looking at the answer in question, it is readable, articulate, and addresses the question. So the appropriate action would be a vote up or down, not a flag or delete vote.
See also the flagging FAQ.
