Hey Solrun, thank you very much for taking the time to play the game and write such a thorough comment!
The chatter is actually unintelligible because it means nothing at all, is just gibberish :)
Jimmy just loves pandas THAT much.
To me it felt natural to press Enter or Spacebar but it would have been better to place some arrows on the screen or to let player just click to advance in the initial comics.
Highlighting the starting position of Marcus is a good idea, could do it in the future.
Also, congrats on beating the game :)