The eBay messaging system was, is and will likely remain the dinosaur that it is. It is just that, a messaging system akin to Twitter with a higher character limitation.
We like to woo customers with proper formatting, fonts, links, pics, etc, as required to answer the question or communicate with them in general, something that is not possible with the system in use now.
We now include our email address and tel. # in the signature field, together with store logo.
There is now also a little flaw in there that works to our advantage and seems to circumvent what would normally be suppressed by the algorithm. I'm sure it will be "fixed" at some point 😄
Bernie