Going off this question: https://community.atlassian.com/t5/Bitbucket-questions/What-HTML-does-BitBucket-support-in-their-READMEs/qaq-p/589154
I was under the impression that snippets also supported html in markdown, but it definitely doesn't as you can see from this post: https://bitbucket.org/smac89/workspace/snippets/M9dgBB
I also don't see the support in a README file in a repository as the documentation says it would.