This should be hidden by the theme styles added in a recent update of
metalsmith-ssg (to v0.1.1)

registration-form.md

@@ -17,6 +17,8 @@ of membership, so applicants must have an existing Open Collective profile, whic
 <div class="formgroup">
 <label for="name">Name <i>(optional)</i></label>
 <input id="name" name="name" type="text" maxlength="40">
+<label for="surname">This should be left unchanged</label>
+<input id="surname" name="surname" type="text" maxlength="40">
 
 <label for="oc-user">OpenCollective user name</label>
 <input id="oc-user" name="oc-user" type="text" required maxlength="15">