That proves my point about how counter-intuitive and badly designed this system is.
When I type the first 2 square brackets a GUI pops up and the square brackets disappear.
This is a bad idea, the brackets shouldn't disappear, ask any UX designer.
Then I type a colon and the box becomes red (which makes me believe something is wrong).
When I type the first letter (the letter "e") the GUI shows me article search results from the wiki I am currently on, even though I already typed a colon.
It is far more likely that I am going to link to a category or another wiki.
The search results disappear again when I have written <nowiki>[[:en:</nowiki> It doesn't give me any search results that are categories or articles on the English Wikipedia.
My father is old, how is he supposed to understand how to use this functionality?
How are people with visual handicaps going to use this GUI?
In the bottom right of the box I am typing this message in there is an icon with 4 square brackets. Of course I assumed that this means (internal) link.
Near the bottom left of the box I am typing in there is a more conventional hyperlink symbol, so I would assume that means external link.