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I like this idea. Some benefits include:
Sometimes users comment useful things instead of fleshing them out into a full answer, whether it's due to lack of time, or not having enough references on hand, or a number of other reasons.
Since moderators are looking to keep comments more cleaned up, it would help separate and streamline discussion by making it easier for such content to go into answers.
It can help decrease the barrier of entry for users who are new to Meta by making it easier for them to share their thoughts, and letting them find posts that they can easily add their own research and ideas to.
Sometimes it just takes a lot of time and people to figure things out