The instructions for handling markup are on the page about preparing for translation, where they belong.
I would still argue that the information belongs on this page as well, at least a mention and link to further information.
I would say that this is even more relevant on this page than on preparing for translation page for the reasons above.
By the way (not directly related to the issue above), I couldn't find the <!--T:n--> tags being mentioned in Edit Markup.
There is already, in the Warning box, a link to EditMarkup and the Typographical_Guidelines. The purpose of that warning is that anyone editing text as described should not be touching the tags at all. I will think about whether it is appropriate to write more about the tags, but it will not be on this page. It is entirely inappropriate to the task.
I have changed the warning slightly.