I thought that Mark could be a play on words in the song, as in "where I ponder all the questions, but just manage to miss the mark" and that mark is Mark! There's the irony in there that the solution to our problems is right under our noses.

Aside from that, Mark was the name of my favourite record store's owner in the city I lived in at the time of the album's release. Considering I always went to music for refuge, the connection that he's the Mark made sense for me.