I knew about the Discourse-specific format, but I was also somehow under the impression that it would - as an intentional behavior - default to just displaying the tag-text for anything that didn’t parse properly in that format as a way of quoting things from outside Discourse?
I guess that I’m incorrect in that belief, and that being the case, the behavior is explained. Although it would be awfully convenient if there was a quote tag equivalent for quoting from extra-Discourse places.