I came here looking to ask about just this issue. Angus, is this an improvement you could implement soon? It really is bothersome and rather embarrassing 
to see event markdown showing up in my mastodon feed. I also use the table of contents liberally on my discourse which also gets exposed markdown.
Because updates also get published to mastodon (which is awesome for wikis!) you can’t even hack this by posting first without the markdown and adding it afterwards.