Hi,
Arlo and myself have been working on a new MediaWiki extension to expose Parsoid's "lint errors" to users.
A little bit of background, Parsoid has a linter that identifies some issues in wikitext that while may not result in user-facing errors, are still not wanted in wikitext. An example might be [[File:Example.png|foo|bar|baz]]. In this case, "foo" and "bar" are ignored, and "baz" is the actual caption - but the bogus image options should be removed. Other errors include missing end tags, obsolete HTML tags, fostered content, etc.
The main advantage of this over tracking categories is that we know the location in the wikitext so it should be easier to identify the error and fix it, as well as knowing whether the issue was caused via a template or not.
The main ticket tracking deployment is https://phabricator.wikimedia.org/T148609.
-- Legoktm