In Spacemacs j and k move the cursor down and up a line on Evil normal state, just like the vim style. 24 j will move down 24 lines just like vim. If this isn't the case, then some custom code has been added or something is broken. C-j and C-k are used to navigate in a helm popup, but I cannot think of another case.

it’s also used in the repl

jk and makes sense, but in vim ctrl p and ctrl n are used to navigate dropdowns and history

I guess fixing it in Helm would have the biggest impact