Public figures, such as politicians, who often talk to the press, sometimes answer "No comment," meaning they are not going to answer the question. It is sometimes an unfriendly answer to a unfriendly question. For example: Reporter: "Have you come to an agreement in the negotiations?" Politician: "No comment." "No comment" is not a complete English sentence, and therefore it is not, strictly, grammatically correct. It is a short version of "I have no comment on that." I believe the reason why the singular, "comment" is used, is because the context is an answer to a single question.

Either can be correct. It depends on the context. "No comment" is more common since it's often used as a fixed expression. People say it when they don't want to answer a question. But you could also say, "There were no comments."

Both "no comment" and "no comments" are grammatically correct and can be used in different contexts. However, the more common usage is "no comment." "No comment" is typically used as a response to a question or statement when someone does not want to provide further information or express an opinion. It is often used by public figures or individuals who want to avoid making a statement or getting involved in a particular issue. On the other hand, "no comments" can be used when referring to the absence of comments in general. For example, if someone is referring to the lack of comments on a blog post or social media post, they might say, "There are no comments on this post." In summary, "no comment" is more commonly used as a response to a question or statement, while "no comments" is used to refer to the absence of comments in a general sense.