https://en.m.wikipedia.org/wiki/User:TheDJ/bgcolor (since fixed since table cells no longer have a default background in minerva)
The TD cell should be green. But in the mobile site it is red. This is because bgcolor is deprecated and unlike style="background-color" does not override skin stylesheets.
I think that this is an argument to make the parser/sanitizer start automatically converting these wikicode attributes into proper inline style attributes. Attributes are very easily overridden by CSS styling, and therefore break easily. With divergent skins on multiple platforms (and lets not even talk about the apps, textextract etc) it's increasingly more difficult to know how your authored wikicode content with attributes is going to look like to a reader.
- T42632: Kill $wgCleanupPresentationalAttributes from MediaWiki core
- T42329: Don't use hacks to replicate a browser function, either let align="" pass through or not; in HTML5
- T48705: Parsoid-based wikitext "linting" tool for "buggy" / "deprecated" wikitext usage; keywords: broken wikitext information