This category is used for minor issues we might discover until we decide it needs its own category. As of August 2018, this category contains one error called "div-span-flip".
Some pages have changed appearance because Tidy used to exchange div and span HTML (https://phabricator.wikimedia.org/T11737). That said, it appears a number of pages listed on there have no real visible rendering impact despite the presence of style and class attributes on the span tag.
Why does this happen?
Tidy exchanged div and span HTML elements so the div wasn't placed inside span. "<span><div>Text here</div></span>" was changed to "<div><span>Text here</span></div>".
This matters only when the span tag had style or class attributes. With Tidy, the style and class attributes had an effect. But, since Remex no longer flips these tags around, the style and class attributes on the span no longer take effect. So, in some cases, this causes visible rendering differences. Linter flags instances only where the span tag had such attributes, but even so, in many cases, there may not be any visible rendering differences.