Thread:Project:Support desk/Unexpected breaks in HTML before closing tags

I'm having a small but challenging issue with some HTML elements (like ordered/unordered lists), and couldn't find a thread about it, so I wanted to see if I could get someone's opinion. It happens when I create any list, like so: Unordered list:
 * Item 1
 * Item 2
 * Item 3

At Wikipedia or here in the MediaWiki Sandbox, the resulting HTML looks like this: Unordered list:  Item 1 Item 2 Item 3 

However, on my own Mediawiki installation, identical input produces differently-formatted HTML, like this: Unordered list:  Something  Something else  Some third thing 

Do you know what might be causing this? Normally I wouldn't be concerned about how the HTML tags are arranged, but in this case the difference is complicating some navbox-related horizontal lists I'm trying to set up. Any guidance would be much appreciated!

MediaWiki = 1.19.1, PHP = 5.4.4, MySQL = 5.5.24. Test page: http://eamononline.com/wiki/Test