Changes
Move "includeonly" tags to category link, not around the whole template. There is no reason not to display an example.
{{fix
|text=citation not found
|date={{{date|}}}
|cat=<includeonly>[[Category:All articles with broken links to citations]]</includeonly>
|link=<!--Template:Fix sfn-->Template:Harvard citation documentation#Wikilink to citation does not work}}<noinclude>
{{Documentation}}
</noinclude>
|text=citation not found
|date={{{date|}}}
|cat=<includeonly>[[Category:All articles with broken links to citations]]</includeonly>
|link=<!--Template:Fix sfn-->Template:Harvard citation documentation#Wikilink to citation does not work}}<noinclude>
{{Documentation}}
</noinclude>