Only those with indefinite leave to remain, so essentially those who have emigrated here and intend to stay. People from those commonwealth countries who share our cultural values and history so why would the Brexiteers object to them voting?
The rule was brought in back in the Windrush era to ensure those who arrived to make a new life in Britain and help us rebuild post war felt a part of the nation. I'm sure the Mail will list all the potential Angolans, Nigerians, Kenyans and Virgin Islanders who can vote but the simple fact is that we don't dish out indefinite leave to remain to Commonwealth citizens any more unless the person ticks multiple boxes in terms of qualifications, wealth etc.
It's BS and they know it but it can always be spun as yet another reason how the liberally biased system does down the poor, hard pressed British man.