Vector is not a responsive skin (does not set the viewport tag), so when viewed on mobile devices, the browser will adapt the content. It will not operate like a narrow screen and our breakpoints will not apply.

Whatever the page loads like will be the minimum zoom level and it won't be possible to zoom out.

What happens?:

Previously before the introduction of table of contents:

Note the line length for the article content is now shorter and crammed to the right.

To fix this we would either need to make the table of contents collapsible, or make the skin responsive.