#healthydebate's been around for a bit but isn't super popular so it's less of a sidebar fixture than #meta, #discuss, or the identity crisis-plagued #explainlikeimfive.
I don't know that extemporaneous posts need a special tag, though. Everybody writes and edits differently, and rigor can easily vary from post to post as well as from person to person. I don't think it's a big deal.
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