I read that as the little blue arrow icon that allows a quick jump to the top of a Page. Shows up when you are scrolling up.
The Aussie ski forum has big blue arrows for both Up and Down jumps. It's very handy. But might be custom programming. They haven't move to 2.x yet because there is so much testing that's required of the custom stuff that's been added to 1.x over the years.
I'll bet he is looking at a phone. The only option on mobile is "Jump to New" which means "take me to the first thing I haven't read yet."
EDIT: I checked it out in XF Support, and it does look like there might be a way. What I found takes up a significant amount of the screen in vertical view, and it adds the extra nav on all screens, not just in the thread view. I'll look into it further, if I can limit it to the thread view, I may go there.
Interesting, good to know. A quick turn of the phone saves some scrolling.
I always wondered if you could change to site to be like TGR...when logged into the site you are automatically taken to the newest post in the tread. Jump to new accomplishes the same, guess I should use that!