<gallery> can be filled with images with the File: prefix, or without it.
When VE opens a page where a gallery has images with no prefixes, it adds prefixes. This bothers people who use wikitext (feedback) because it "complexifies the code".
Would it be possible to have VE not adding the prefixes when they are omitted in the wikitext?
The other solution would be to remove the ability to have galleries displayed without the prefix, to have consistency on how images are displayed.