Thanks Mario, that was really helpful. :)
Here's what ended up working for me (referring to the same NewEssayTemplate):
<<tiddler {{tiddler.title+"##code"}}>>
!code<script label="New Essay" title="Create a new Essay topic">
var alwaysTag="EssayTitles";
var title=prompt("Please enter your new essay title","Another Dumb Essay");
var mytext=store.getTiddlerText("NewEssayTemplate")
var tags=[alwaysTag, "anyTag"];
store.saveTiddler(
title,
title,
mytext,
config.options.txtUserName,
new Date(),
tags);
story.displayTiddler(null,title);
</script>
I think it works over the other because it writes the tiddler directly instead of opening it for editing, where the previous version got the title wikified "twice"