Thank you for this. However, this is intentional - otherwise, it would not be a link to the file, it'd be a transclusion of the image, which will be done differently (an insertion inspector). Links to pages should not accidentally become images for users who do not (and should not) understand the way that wikitext expects that.

Marking as WONTFIX.

Well, our rendering differs from the PHP parser.

We could still support the same rendering by making the serializer clever enough to re-add the colon to the text before checking the link content for changes.

Low priority for now, but something we should support eventually.

Fix pushed for review in https://gerrit.wikimedia.org/r/#/c/43598/.