HTML/Markdown used dynamic content does not render in trigger emails
Dynamic content supports using HTML and Markdown however there are limitations when a dynamic content placeholder is used in the trigger message body that will be sent in emails. Markdown and HTML from dynamic content are supported in the ticket comment body, but will not render when the dynamic content placeholder is used in the trigger message body and then sent in Support email notifications. Instead, it is recommended to use HTML in the trigger body to add formatting to emails. Markdown and HTML from dynamic content will render in macros due to being in the ticket comment body.
We discuss where HTML and Markdown can be used in Zendesk Support here.