This only "works" (breaks) on newly inserted images.
- "Insert" > "Media".
- Choose a file and "Use this image".
- Write a caption.
- Add a wikilink to the caption ("[[example]]").
- Before clicking "Insert" for the image, select the newly created link. Open the link (e.g., right-click the link in the context menu) and open it in a new tab.
Result:
If you start in a /subpage, then the link goes to https://en.wikipedia.org/wiki/User:Whatamidoing_(WMF)/example (case sensitive). Another editor reported a link of en.wikipedia.org/w/linkname instead of en.wikipedia.org/wiki/linkname. See original report.