Yes, as it is now it's unreadable, I came here to make the same point. Tilted to the right starting above their column would make the most sense. I can barely read text in it's current orientation let alone regex's.
On either side of the "validate" button at the bottom are controls to rotate the puzzle to this end.
That's still not acceptable, now it's harder to read both.
Considering that (from their stats page), 15k people have answered 326k puzzles, I'm pretty sure it's "acceptable" to somebody.
Those buttons could do with a 'position: relative; z-index: 1' so they are still easy to click when the table is rotated and overlaps them.
Edit: Coworker pointed out you can rotate the board to read it better.