URIs begining with "ftp://" protocol distinction are invariably formatted in the following wrong way:
Page source:
ftp://sample.com
[[ftp://sample.com]]
[[ftp://sample.com|sample ftp site]]
Output:
<a href="ftp://ftp//sample.com (...)>ftp://sample.com</a>
<a href="ftp://ftp//sample.com (...)>ftp://sample.com</a>
<a href="ftp://ftp//sample.com (...)>sample ftp site</a>
Unless I'm missing something there's no way to enter an ftp:// URI, except as %%-enclosed plain-text.
One would expect that dokuwiki's automagical link formatting would only apply to protocols it handles properly. Either the protocol should be properly formatted or it should not be automagically formatted at all.