Yes. Under each comment, a Reply option lets you open a thread, just like on social media. Replies appear grouped under the original comment.
It's very handy for answering questions about an item: availability, dimensions, condition, pickup spot.
- The person involved may receive a push notification of your reply.
- For a private discussion (negotiation, contact details), use Messages instead.
Keep in mind that replies and comments are public: don't share sensitive information in a comment thread.