Traditionally Wikipedia articles have used :<math>...</math> for indentation, which creates a definition list (a "description" with no corresponding "term"). Because this supposedly causes issues for some screen readers, several years ago a "block" mode was added to the math plugin, invoked via the wiki markup <math display=block> ... </math>.

When colon-indented :<math> is used, the result is a block element which takes up as much width as the content rendered by the LaTeX inside. When it would collide with a floating image on the right, the math will be pushed down the page until it can fit entirely. Sometimes this results in some extra whitespace but at least the formula is always legible.

When such formulas are replaced with <math display=block>, they are no longer correctly pushed below floating images they would collide with. Instead the CSS is set up so that the math box will take only as much horizontal space as is available and then display a scrollbar for a reader to view the rest of the content of the math box by scrolling to the right.

This causes a severe problem on displays of moderate width (e.g. a laptop trying to show two Wikipedia windows side by side or a narrow tablet), because floating images will sometimes take up most of the width of the content view, leaving only a skinny part for paragraphs of text or math (etc.) on the left. For text this is moderately annoying but mostly okay, because the text will reflow, so sometimes only a few words will render per line, but all the text will still be visible, just with more line breaks than ideal. For <math display=block> the result is at best ugly and at worst completely crippling. Sometimes barely any of the formula will show, forcing the reader to scroll a skinny sliver of "content box" past a very wide formula.

The only workaround is to never put formulas near to floating images. This is a very annoying burden to place on wiki authors, because the problematic collisions only occur with some (but not the most common) display widths, so in general they don't notice the problem. Then readers with an unlucky display width just find the formula unhappily unreadable. Figuring out how to rearrange formulas and images to avoid the issue is error prone and fiddly, and sometimes impossible without resorting to massive amounts of unnecessary whitespace.

Ideally these math boxes would push down the page until they can fit. The side scrolling can be reserved for cases when the math content still doesn't fit within the width of the window even when there are no floating images.