On mobile (or small viewport), the legend to the right of the "Top 10 by edits" and "Top 10 by added text" is squished up against the right. It should wrap and be shown below the chart.

Example: https://xtools.wmflabs.org/articleinfo/en.wikipedia.org/Hanksy#top-editors, then reduce the size of the browser window.

CSS for this tool is at https://github.com/x-tools/xtools/blob/master/web/static/css/articleinfo.scss

I'm pretty sure there is a flexbox-y way to make it wrap, but you could probably also throw some simple CSS in the @media (max-width: $bootstrap-sm) { block.