A reader mode like Safari  and Firefox  will improve the user experience in many cases.
Here the web designer make two major mistakes that hurts readability:
- Thin typography
- Low-contrast font color 
Maybe at first glance you detect the readability problem but say that is no major issue, well, reading a whole article can create vision fatigue, and for example elderly users with bad vision can’t even read it.
The web have many sites with this problems, reader mode is a way to give the users more power.
Seems like a reader mode is a common request for Chrome users .
Chrome browser has 50% market share right now , introduce the feature will be another advantage for Brave besides the in built ad/spy blocker.
Opinion: Chrome plans to introduce an in-built adblocker in 2018  and for many users will be no reason to use Brave, besides the Chrome adblocker will accept “good” ads, the adblocker feature will be not the exclusive killer feature of Brave anymore (like Firefox tabs in the IE era).
Sources here because seems like I’m not allowed to put more than one link