"Cotton-pencil-diamond tribondThree things: Cotton, Pencil, Diamond. What do they all have in common?". I replied to this question: "They have in common the letter 'n' in their name." This answer has a score of -2 (on 2016-08-22) and was deleted after two days by a moderator (@GentlePurpleRain) who left the comment "The goal and purpose of this site is to gather quality answers to quality questions. This answer is obviously not intended as a quality answer, and thus is being deleted." and "Why was your post deleted? See the help center". I checked the link and cannot find a reason that justifies this deletion (except that "Moderators can delete any answer". Am I actually at the moderators's mercy and must accept the impertinent justification that my answer is not intended as quality answer?
You posted your answer after the question already had an accepted answer.
Your comment on your answer:
the question had already an accepted answer when I posted my answer. The answers to a question are not defined by the poser of the question but by the question.
What I gathered from this is that you were attempting to draw attention to the (alleged) poor quality of the question by posting a "joke" answer of sorts. While the answer is technically correct, it would be hard for anyone to believe that it was the intended answer to the puzzle. It was poorly received, and had a score of -3 when it was deleted.
Posting answers like this is not helpful in improving the quality of questions. We end up with a poor question and a poor answer, instead of just a poor question. It further decreases the quality of the site.
If you disapprove of a question, you can downvote it, or vote to close if you feel it doesn't fit the guidelines for this site, but please don't contribute more low-quality content.