Ha, yeah I think it's my vim muscle memory that made it feel so weird. `j` going left instead of down and `k` going right instead of up. `h` and 'l` probably would have made me feel right at home though. (And in fairness, changing the keys is trivial in this case!) :-p
Those are Vim bindings. The J key rests right under your index finger (and it’s easy to find it thanks to the nudge on your key), which enables you to spend little to no energy to “scroll down”; the K key is for scrolling up.