It absolutely is! If you have any Polish/code-breaking skills, I'd love to see what you can come up with. The Poles were the great unsung cryptanalysts of the Second World War — they can be great again!
Damn, the mystery continues! If it was a scavenger hunt or something (and it's not a simple substitution) then I guess the chances aren't high that we might figure it out. Still, it would be amazing if we could find any new clues after all this time. Let me know if you find anything.
I can't believe it was just for the lulz — they went to so much effort, with the whole page of hand-drawn letters, and these things were plastered all over the street. If it was just gibberish, they put a ton of work into it. I don't think I'd mind being had, though. If they went to that much effort, they earned their victory.