I recall seeing some of the symbols and made nothing of it. Then article last year breaking some of these symbols down and a riddle was revealed.
http://www.kotaku.com.au/2011/07/the-trials-hd-riddle/ (http://www.kotaku.com.au/2011/07/the-trials-hd-riddle/)
If you thought the extrerme levels in the game were difficult... Heck most people, including myself had no idea what the heck was going on until the article came out.
So it appears nobody ever figured out the riddle on the Red Lynx forums so they figured an answer should be revealed before Evo comes out in teo days.
Trials HD - The Riddle Revealed (http://www.youtube.com/watch?v=Yg4lg7T7Zgs#ws)
Gotta be one of the coolest easter eggs in videogame history.