[deleted] I have already tested it at my forum. You can't just include the script there because the script does not handle Flarum's dynamic post rendering.
In the picture above, the render works fine in static footer (because it's not changed since first page load), but not in the post (since the content of the post is loaded a while after page loads). It also isn't rendered when you are writing the post, so I think that a "cheap" way like this isn't possible. Technically you could make a function that runs every ~ 3 seconds to re-render the page, but that is very inefficient and an extension would be a better way to handle this IMO
