But since embed uses an iframe, Discourse seems to suppress it. Is there a way we could somehow whitelist this so people could include runnable code snippets in their posts?
We recommend codepen instead, which should already work.
You would either need to make a plugin for it, or send through a PR to the onebox gem to optionally allow this embedding (default off)
OK - thanks for clarifying. I will reach out to REPL.it and see if they can add themselves to OneBox.