now that R+L=J is confirmed, would the people of the north still follow him, knowing he is the grandson of the mad king (bastard or not)? yes, he may have stark's blood, but half his blood is targaryen, and the north are not too fond of targaryens.

btw, i wonder if master aemon (last maester of castle black) realized that jon was his relative which renders his reference as "the last targaryen in westeros" moot?

jon is son of rhaegar, son of aerys II (mad king), son of aegon V, little brother to maester aemon.