Prevent conditional comments being stripped out in email template?

I spent two days trying to figure out why parts of an email template I'm developing weren't displaying correctly in Outlook, and I finally discovered that Marketo is stripping out the Microsoft conditional comments (e.g. <!--[if mso]>...<![endif]-->) that target Outlook's rendering limitations. I did some experimeting, and Marketo does not strip them out if they are added to an editable region when editting an email under Marketing Activites. They only seem to be stripped out when they are part of the email template.

Has anyone else run into this issue, and are there any workarounds? I consider this a pretty big limitation in Marketo's email templating system (right up there with the lack of automatic CSS inlining).