Thread:Project:Support desk/Closing tag is broken

You can make dialogs in MediaWiki sites by using the  tag with the   parameter, allowing you to use CSS to configure the styles. The problem is: the closing tag sometimes won't work. My code for MediaWiki:Noarticletext is:

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When previewing the page, MediaWiki refuses to close the tag, and instead displays the closing tag in the resulting document (the tag still will work without a closing tag). Help?