(What!? Derpibooru had keyboard shortcuts!?)
YES! It did! And it still does! But now they’re different, bigger, meaner, MORE FANTASTIC!
Scroll down to the bottom of the page and click the “Keyboard shortcuts” URL, or just go here: https://derpiboo.ru/shortcuts
You don’t need to hold any special modifier keys (like control or alt) to use the shortcuts. Just make sure your cursor is outside of a text entry box, and press the key!
vim really has nothing to do with it - these are just the keys everyone ended up using as a standard for next/prev on the intertubes, and they make sense (aren’t used elsewhere). Arrow keys were causing issues because people with smaller displays couldn’t scroll sideways on pages for larger images with them, hence the change.
Apparently these new shortcuts are meant to reflect the VIM standards (a popular text editor with programmers), they seem to be the same as the shortcuts from github. If you really want the old shortcuts back you can talk to the admins about it. There’s usually at least one moderator/admin around in the IRC channel.
What the fuck, guys!?