Snippet comments don't appear to render front-end GFM
@katwu caught that Mermaid diagrams don't seem to be rendered in snippet comments, and indeed this is easy to reproduce:
{width=774 height=600}
Note that they render fine in the snippet itself, but the Mermaid block in the comment isn't touched after backend processing.
Live test at: https://gitlab.com/gitlab-org/gitlab/-/snippets/5969830