@Saoiray,
I believe this is the intended behavior of the site. This second scroll bar appears to track where you are within the Reddit thread itself (observe that only the inner-most bar scrolls up/down while in an article) whereas the first/original scroll bar marks the position of where you are within the Subreddit.
Oh I see now what you are saying. I tested this in Chrome and am not seeing the second scroll bar appear. Good catch. Not sure how dire of an issue it is but I will raise it with @fanboynz regardless and see if we can find out why.
@fanboynz Whatever comes with the browser by default. To be honest, I’m not even sure if I know how to switch to anything else. I found it once but couldn’t tell you from the top of my head where that was. Also not sure if multiple options are available for all OS? Such as when I have talked to you about issues on iPhone. Or which devices can opt into the others.