[-] collapses the replies so that you can easily see what's next. On reddit the equivalent functionality is a button literally called "hide child comments."
But as another comment mentioned, you can click root | parent | prev | next to get navigated through the thread. Personally, I prefer the collapse, though, as having the top of my screen move without my direct control is a bit jarring, but there's more functionality from these buttons.
But as another comment mentioned, you can click root | parent | prev | next to get navigated through the thread. Personally, I prefer the collapse, though, as having the top of my screen move without my direct control is a bit jarring, but there's more functionality from these buttons.