Number 6 is terrible -- hacking together html from strings is just not the right away to do it. He should be generating the DOM elements and appending/nesting the generated elements appropriately, not concatenating a messy string.
Also, using DOM methods allows you to easier attach listeners, save references to DOM elements for later updates/use etc. That means less getElementById()'s later.
Writing HTML inside js code is just horrible (IMHO). Horrible ugly code. And obviously easier to have security issues if you're including non-sanitized user data.
#6 is a horrible idea.
As far as your JS code is concerned, HTML is a (horrible, ugly) serialization of the DOM. Manipulate the DOM programatically. Don't use HTML.
innerHTML is just the worst thing ever invented. Ugly ugly thing.
<script type="text/html" id="user_tmpl">
<% for ( var i = 0; i < users.length; i++ ) { %>
<li><a href="<%=users[i].url%>"><%=users[i].name%></a></li>
<% } %>
</script>
This is quick and dirty, but much more elegant than writing HTML in JS.
Especially when working with something like json data generated elsewhere.