Jay’s covered some good reasons not to do this. I have a similar use case, but you’d be surprised how many Topics exist. Plus, if you make an FAQ, that Topic would now be a Question. If you made a Beginners Guide, that would also be a question.
Consider also the language: “Topic” inherently includes the type “Question”.
Topic: a matter dealt with in a text, discourse, or conversation; a subject.
Question: a matter requiring resolution or discussion.
As an achievable alternative, which aligns with language and nudges users towards your Q&A style, it’s possible to replace “Replies” with “Answers” without much pain.
