Template:!
From Kerbal Space Program Wiki
|
{{!}}
is used to encode "|"(pipe or vertical bar) within template parameters. It is used for things such as passing table syntax to templates.
In theory, this template is obsolete as of MediaWiki 1.24, having been replaced by a magic word. Pages should no longer be able to transclude it via the normal method.
This template should probably remain forever to avoid confusion about how something which looks like a template is working after being deleted. It also serves to point them in the direction of the documentation.