I propose that we add, somewhere in the UI, some indication that there are keyboard shortcuts. This will likely improve the chance that someone will know of their existence and benefit from them.
Ideally, I should not have to search somewhere about keyboard shortcuts to know that they exist in the first place.
One suggestion: on the help button on top right, add a new section "keyboard shortcuts". When pressed, the shortcuts to access each part of the UI are shown overlayed on the website, showing how to access each of the components through them.
Another suggestion: when a user reaches X reputation, add it as a functionality to the user (with a respective indication on the promotion). This avoids new users being overwhelmed by new features on the start, and at the same time increases exposure of this functionality when users become more used to the website.
I am not expert in UX, so I am not the best person to provide solutions. Still, my main point is that keyboard shortcuts are difficult to find/know about their existence.