Cannot get <details> <summary> in Laracasts discussion

I cannot seem to get <details><summary> markdown blocks working in the Laracast's Discussion markdown. As seen here: https://gist.github.com/ericclemmons/b146fe5da72ca1f706b2ef72a20ac39d

It would be really useful to hide massive stack traces / logs / code blocks and keep the attention on the issue.

Am I doing it wrong, or is it not supported?