Put this another way: lots of people don't have a second thought about telling this /extremely successful/ project how it really should have been run.
So
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Indented text is rendered in verbatim monospaceBut its only a very limited subset of it. For example I cannot do [thing](url) URL links like you can on reddit. Anyone implementing a comment system that wants rich text should be using it, though, if a WYSIWYG editor is too much, or if its targeting a technical crowd.
HN only supports the two formatting types you described, plus auto-linking of URLs written out in full, such as the one in the previous paragraph.