Is there any way to insert html into my custom warning messages?

Is there any way to insert html into my custom warning messages?

I want to make my error message for duplicate entries display a list of options for the user below, in a "UL" element. When I enter the tags, they are sanitized out. So far, I've succeeded by replacing the opening bracket of the tags with an "lt" character reference, but whenever I want to change the message, I have to re-enter them.

Unfortunately, HTML elements in the form warnings will be stripped off for security reasons. I'm afraid that will not be supported. Sorry about that.