Example: https://en.wikipedia.org/w/index.php?title=Special%3AAllMessages&prefix=E&filter=modified&lang=en&limit=1000

Desired outcome: Some method for troubleshooting the markup. Is [[Help:Edit conflict]] a blue link? Is {{#titleparts: an available function with all required parameters populated?

Actual outcome: The message wikitext is in raw form. Validation can be performed only with laborious workarounds, such as opening each message in a new browser tab and clicking the preview buttons.

Environment: live enwiki, which is

• MediaWiki 1.31.0-wmf.23 (rMW82d9536b5880)
• HHVM 3.18.6-dev (srv)
• MariaDB 10.0.33-MariaDB

Interface messages are critical for providing targeted information, especially to new editors or those attempting unfamiliar tasks. On small third-party wikis, they often communicate vital policy points or behavioral expectations to new or occasional users, because:

• Resources are insufficient to mentor newcomers individually.
• Policies and social norms vary widely among communities, and the wiki's power users may not have written thorough documentation specific to their group. (Due to the ubiquity of Wikipedia, I often hear newcomers assume that all wikis simply inherit its infrastructure!)
• The community may have a preexisting social media platform, and the newcomer spends most of their time there, thus not retaining the wiki's procedures and expectations from session to session even in good faith.

For these reasons, textual problems which would be tolerated on a content page (redlinks, markup errors, flawed template logic) are harmful in the interface. They confuse newcomers and may even lower morale -- if a help desk or an explanation of admin duties is a red link, maybe there is no one to help or to act as a responsible admin? After an extension install or a MediaWiki upgrade, power users should have some method for batch-reviewing everything immediately, rather than waiting to stumble across an issue months later.

I am certain that such issues do not affect enwiki: the law of large numbers virtually guarantees that some end user will show initiative and report them, and that an active noticeboard exists to escalate them. It took a while to find even the superficially concerning examples above (which I already knew were correct when rendered), but flipping through some non-WMF sites, I soon see

• https://goldensunwiki.net/wiki/MediaWiki:Revdelete-confirm (redlink to policy hub -- ouch)
• http://tfwiki.net/wiki/Special:ListGroupRights (redlink in MediaWiki:Listgrouprights-summary)
• https://fireemblemwiki.org/wiki/Special:ReplaceText (redlink in MediaWiki:Badaccess-groups)
• https://www.wikibound.info/wiki/MediaWiki:Apihelp-query%2Biwbacklinks-example-generator (undefined interwiki prefix "wikibooks")
• https://www.grandtheftwiki.com/MediaWiki:Checkuser-toollinks ("Tor check" is a stale external link)

The title of this ticket is only one possible approach, and perhaps another would be better, or at least less expensive (the load time of Special:AllMessages is already considered non-ideal, e.g. T9925#117155). Even if it were implemented, messages with parameters might remain somewhat opaque (unless the admin had every special page memorized), but T76428 would help greatly with that.

(EDIT: fixed tags. How did I do that?)

Hope this all makes some sense and isn't too soapboxy; thanks.