Hi Richard,
I have a form in a page where people licence stock footage through it. Some people doesn't really know what some of the dropdown options mean, so I wanted to add a "(?)" with detailed information about them. A pop-up would open when clicking on it, for that I need HTML.
Just after posting this I realized I could use other plugin I have installed right now called prettyPhoto Media and I solved my issue with that.
Still I think it would be useful to be able to add some HTML to any Jetpack form.
Thanks
PS: I just posted a request on GitHub.