If you want to have pre-prepared messages that you expect to copy and paste as a comment multiple times, feel free to post them below. For example, a new user wanting to ask an off-topic question.
New user asks a question about learning techniques for [topic], or some other off-topic question
Good on you for wanting to learn Japanese, and thanks for joining Japanese Language and Usage. Unfortunately, this question is off-topic, for reasons explained here [change link depending on what kind of off-topic it is]. There's a post on the meta site on resources for learning Japanese, and you are welcome to ask about [topic], and anything else within reason in the chat room, even though it's off-topic here. Feel free to ask other questions on the Japanese Language and Usage web site in the future. Ganbatte! (Don't give up!)