1. Put cursor inside a link that has link text containing at least two words (e.g. equiv of [[Foo bar ]])
2. Select first word.
3. Type another word in its place. Observe how this new text is (correctly; as expected) part of the same link as before.
4. Move cursor elsewhere in document (or; Click on Save page).
The text that was added is now no longer a link.
Replacing words at the start and end of a link label has been a long-time problem in VisualEditor. I was glad to see this finally work, but somehow it didn't work all the way.