Ultimately everything can be done. But my idea was to make the keyboard the least intrusive as possible considering that it stays over your content. I would rather see the terminal's text then the key's edges in those pixels that make up the edge line.
Again, my idea is that if you type exactly on the symbol then you will for sure press the key in the best location possible: in the center of it. If you see the key's edge or not, in this case, is irrelevant.

In the end, everything can be customizable. Some people might want edges, some not. We can for sure offer them.