Thank you all for the comments and feedback! I've uploaded an update that disables the diagonal movement, as that wasn't intended to be possible.
There seems to still be some glitches with the character's rotation occasionally, but they do not appear for me in engine so I think it's wonkyiness on the html5 export side :/
I also added arrow key support in case that is more intuitive for some, but be warned that the up/down keys make the page scroll, which gets pretty annoying.
The overall unintuitiveness of WASD in isometric view was just poor planning on my part, but all in all thank you so much for testing this game out!