I’m drifting toward off topic here, but HTML is not an issue IMO. But short codes are if a wordpress-post is shown as text on Discourse, because those are stripped off.
I kind of could imagine why this is happening and that’s why I can’t count it as a bug or similar, it is just another limitation.
But I haven’t had any issues with HTML per se. But WordPress itself, depending of theme I guess, will strip off html from excerps quite often, though.