These aren't visible in the output, except as fallbacks to "alt". We should stop doing that and get content to move them to explicit |alt= options.
What to do for alt?
- Core has a fallback to use the caption as the alt text when no alt is provided, and a further fallback to the filename if none of those are present
- Parsoid, for its part, only adds an alt if it's explicitly requested with an |alt= option
- This was decided in https://phabricator.wikimedia.org/T50958#534409 with clarifying omitting the further fallback to the filename in https://phabricator.wikimedia.org/T50958#534442
- The idea was for one source of truth for editability, and I guess some sort of post-processing can fill things in as needed for acessibility
- We can create a linting category for inline images with a caption without an alt and then make the change in core to be more like Parsoid
- Longer term, description stored with images seems like the better place for alts fallbacks but that has the editability/truth complications https://phabricator.wikimedia.org/T63566