I had no idea this was happening, how did you test this?
The player sprite moves visibly faster in the diagonal directions. You can tell by letting an army follow you first in the cardinal directions, and as soon as you start going diagonally, they fall behind (and de-spawn).
The red area to the south-east kills me when i try to walk into it, happened on seweral occasions.
I'm glad you appreciated the thoughts and tips. =)