@Itod, so in your opinion the "The_____iskeyfile" message is the intended message?
Well, I have a theory didn't want to mention before while trying to find the proof. The message "THE
fm_aurISKEYFILE" can hardly be a collision, and the bold scrambled part is intentionally left there to be de-scrambled in the same way other bit-streams should be de-scrambled to get a key. If you come across the stream of bytes from private key you may not notice something is scrambled, but if you find something like plaintext quoted above it's pretty obvious something is wrong. So to answer you: yes I think it's intentionally left there scrambled/corrupted to show the way.
Anything can be the way to de-scramble it in a coherent message.
you don't have to search in the board tiles to de-scramble that message.
it's only 5 letters so it would be so easy to get all meaningful words from it.