I'm going to be assertive and marking this as a Bug rather than an Improvement.

Atlassian needs to support Markdown as a commenting markup language; it is the de facto markup language used online in many cases (bitbucket, github, reddit, stackoverflow) and honestly has a much cleaner design with fewer edge cases than the "wiki markup" used in Confluence and JIRA.

Stash comments allow the use of Markdown. We are considering using Crucible, only because of Stash's shortcomings... and now here I am reporting a shortcoming in Crucible that is addressed by Stash.