I think you've answered your own question. I just flagged a new post on the Quest board (probably the same one you did) as it was not a suitable quest topic as I understand that Board and likewise encountered same limitations.
Apparently so. It's just another regrettable feature of that ill-conceived, inappropriately-named board. That raw rice question, a medical one, has no place on CH in the first place, but if it DID, it would NOT be on Food Quests.