This:
{{#tag:section||begin={{PAGENAME}}}}
might reasonably be expected to produce this (with the page name expanded):
<section begin={{PAGENAME}} />
Instead, it probably produces this (with the page name expanded):
<section begin={{PAGENAME}}></section>
These tags are from the Labeled Section Transclusion extension (LST):
http://www.mediawiki.org/wiki/Extension:Labeled_Section_Transclusion
LST requires self-closing XHTML-style tags in order to function correctly, but #tag does not seem to have any means of providing that capability. I would expect that either it would do it by default when the content parameter of #tag is empty, or perhaps when some parameter flag is present, maybe like this with a "close" parameter:
{{#tag:section||begin={{PAGENAME}}|close}}
If the empty opening and closing tag behavior has no function, then maybe it would be better to change it to produce a self closing tag by default instead. If I understand it correctly, I think the XHTML and XML W3C specification allows all tags to be self-closing if empty. I'm not sure if there's any official preference though, since these are totally equivalent as far as I know:
<...></...>
and
<... />
Version: master
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