Another common issue is templates is with the syntax [[:{{{1}}}|{{{1}}}]],
where {{{1}}} is a page title that might be prefixed with a colon. This is
often found in templates like {{softredirect}} or {{main}}.
I'm afraid the simplest solution is:
{{#ifeq:{{padleft:|1|{{{1}}}}}|:|[[{{{1}}}]]|[[:{{{1}}}]]}}
This generates a normal link is the parameter {{{1}}} starts with a colon
character, and a colon-prefix link otherwise.
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Matma Rex