The code that builds this dropdown has been copied from DeleteAction to the RevisionCommentSupplement extension (incorrectly), Translate, and now, Nuke (see https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Nuke/+/758037). Complicating matters, it's also used in FileDeleteAction but with different messages using inheritance and constant overrides.
Codesearch: https://codesearch.wmcloud.org/search/?q=deletereason-dropdown&i=nope&files=.php%24&excludeFiles=&repos=
This code should be refactored so extensions can reuse this without having to reimplement/copy it all.
