We don't have any connection whatsoever with any person who decides to be in charge of the lines... these "line-mods" are totally and completely self appointed and normally they appear the very moment the line starts (more usual than not is them who starts the line). Neither us nor u2.com have any say or input on how the lines are arranged... it's first and foremost a fan made thing.,,
Our responsibility starts and ends in the board and the site (being this Zootopia / u2.com) - we don't oversee anything outside the board, with no exceptions...
Be aware that not every person at the line would necessarily be an U2.com member, so asking only here for guidelines and policing wouldn't be effective...
What can be done in advance would be posting messages with the goal to create awareness, in the hope that people listen and act like human beings towards the other person in the line, being them abled or disabled...