It depends on the ```DOCTYPE``` (and, as it turns out, Katello doesn't have one specified, see #3057).  

In HTML5 self closing tags are valid:  http://www.w3.org/TR/html5/syntax.html#void-elements

In XHTML it's valid.

In HTML4 it doesn't work.

I could remove it to be safe if we wanted, I'm pretty sure my IDE added it.