While typing [[User:Username|]] into an edit summary may, as indicated, successfully notify the user, its inclusion as an example at Help:Notifications/Types#Mentions in edit summary gives the impression that an editor would use it. That, in turn, may raise the expectation the empty pipe works for the purpose intended, to hide "User:" from the text. But the empty pipe trick doesn't work in edit summaries, yielding the same result as [[User:Username]] without the pipe character. So, though it isn't exactly doing any harm, I propose we remove that example as mildly deceptive or confusing, leaving only [[User:Username]] and [[User:Username|Username]].
Topic on Help talk:Notifications/Types
Hello
I rely on your tests. :)
I edited the help page. However, instead of removing the example, I've detailed what it does. It is better to explain all cases than removing things and have them being undocumented.
Thanks. I think it needs a tweak--it doesn't appear as [[User:Username]] in the history, as you wrote it. It's that it displays as a link with the text "User:Username" rather than just "Username" as would be expected by someone familiar with empty pipes from their use on Talk pages. I'd change it myself but I don't know the convention to follow for formatting these links in this context.
Correct! I typed too fast. :)
Thank you very much for your help!