Note MF is currentlly at V 13.
Yes, you can use HTML in your custom emails;
http://help.machform.com/m/using-machform/l/556233-sending-auto-responder-email
If you note in the screenshot, the checkbox option that says "Send email as plain text"..... this suggests the default format will be HTML unless you specify otherwise. Whether using the auto-responders in a logic rule or just using the default responder message mechanism, creating the custom messages is the same.
So try it out - simple markup like bold tags like <strong>, </strong>. I'm not sure how elaborate you can be, but I'm sure you can design a reasonably simple email template, with the field place holders included.