Hi @Shawn Weeks
I know it accepts HTML - or at least used to (we aren't on 8.8 yet) - and the documentation for configuration also mentions HTML.
I assume given the text is bold on your admin console below the edit box you've pressed the blue rectangle to show what your text will look like as a preview? And it appears to work?
According to this answer the options available can differ between instances - I'd suggest using HTML as a preferred option but if you'd like to get more information on this for your instance, I'd advise contacting https://support.atlassian.com/
Edit: Checked, this is a reported bug - see JRASERVER-67422 - HTML is the workaround.
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