By default Desk formats emails in a WYSIWYG (“what you see is what you get”) editor as HTML, but if you prefer you can also use Markdown for writing emails and Helpdocs pages.
In Markdown you would for example type
**Hello** which then shows up as
Hello. Many people find this faster and more convenient.
You can find an overview and quick tutorial on the Markdown home page. There is also a cheatsheet with the most important format characters in the top-right corner of the edit field.
For emails the default for new users can be set in the company settings; in addition, every user set their personal preference in their profile. Changing the company setting will not change the setting for any users – it’s just a default for new users.
Note: Desk will never convert HTML to Markdown or vice versa, so if some users use Markdown they may occasionally see the HTML editor when editing messages written as HTML or when loading drafts saved as HTML.
For the Helpdocs you can set the default per site, which can be overridden for every article. Changing the site default won’t change any of the articles.
Canned responses, autoreply, etc. are currently always in HTML.