Hi Adam. Would you mind emailing into our support team at firstname.lastname@example.org? We'd love to help fix this problem, but can better track and manage it through our official support channels (of which Community is not one). Thanks!
An infographic of email limitations (and possibilities) is an exceptional idea! Education for stakeholders and non-email geeks is definitely one of the best ways to set expectations and prevent fails from going out the door. In my previous agency life, I had my own guide called Jason's Little Guide to HTML Email that I shared around. In retrospect, an infographic probably would have worked a lot better.
I like the tip for having someone not involved with a campaign QA it. Sometimes all that's needed is a fresh set of eyes!
Haha, glad to hear it, John! It's actually a new version of a resource I had out for a long time. Explore the rest of that site, too ;-) It has some educational products I'm working on, the first of which will be out on November 1st.