Steps to reproduce:
- Copy the URL to an article on English Wikipedia (https://en.wikipedia.org/wiki/Foo)
- go to another wiki than English Wikipedia
- create a link with the URL you have copyied (labelled "Test" on my example)
Expectation: [https://en.wikipedia.org/wiki/Foo Test] or [[:en:Foo|Test]]
If I create on English Wikipedia a link to a French Wikipedia article, the link is rendered well.