It became obvious that something was going to need to be done if we were going to work with a specialist like this. It occurred to us that the ASP.NET rendering engine allows us to create server side comments that are not transmitted to the client. That helped keep the HTML clean on the client and allowed us to indicate to our specialist that there was a div or span that is needed (and shouldn’t be optimised away)
<div id="sizeSurchargesInfo"><%-- Populated by an AJAX Callback --%></div>
In hindsight, it seems rather obvious to simply comment the code. However, in these enlightened times it does seem unnecessarily frowned upon.