The specific website in question has the article written twice on their website. The first time is for the regular desktop website and the second is for "legacy mobile". The duplicated text is hidden from view.

However, Firefox Reader View is detecting the duplicate hidden text and displaying it.

This is an issue with the website design.

I see the same happen.

If I look at the page source then I see that the article is present twice, one legacy version for mobile and a second version for desktop. Firefox shows them both and doesn't seem to honor that one is hidden (display:none).

Found a similar bug, so apparently this hasn't been fixed properly.

• Bug 1430493 - In reader view, latex formulas/equations are doubled (should remove items that have inline style="display: none")
• https://github.com/mozilla/readability/pull/285