This template produces a link in internal link style and also a "hidden external link", to allow it to be found by Special:Linksearch, which, unlike Special:Whatlinkshere, is specific for the target section. This backlink requires that the extension Special:Linksearch has been installed, which is the case on Joomla! Documentation.
Do not put "#" at the start of the anchor.
ml|Help:Link}} gives Help:Link
ml|Help:Link|Section linking (anchors)}} gives Help:Link#Section linking (anchors)
ml|Help:Link||label}} gives label
ml|Help:Link|Section linking (anchors)|label}} gives label
ml|a}} gives A
ml|:a}} gives [[
Undefined parameter giving odd result: