In my view it would be better for shop and rail staff to avoid actively challenging individuals. It is not their job to enforce and that is reflected by the policy of the majority of TOCs and supermarkets. So long as signs are displayed, appropriate announcements made etc., anyone not wearing a covering should simply be assumed to be exempt.
Which means the system is less effective, as then those who could wear coverings but don't like it then don't. And many such people are younger and so less likely to distance and so pose a greater risk.
The mind boggles as to why those with genuine exemptions don't want those exemptions keeping for them. After all, if everyone who is not exempt wears a covering, it's safer for those who can't, too.
If you were in a wheelchair, say, and needed the loo, would you be particularly happy that I'd decided to take the Daily Telegraph into the disabled cubicle just because I felt like, and so you'd have to wait? I bet you wouldn't. Or that if you needed to use your Blue Badge to park next to the supermarket, that I'd parked there "just for a minute"? I bet you wouldn't, and again quite rightly so.
I suspect some of those shouting about it in here are people who wouldn't get an exemption if it had to be given formally, though?
I know some of you don't want masks. But if we are going to have them, and the Government has decided we are, then to me it really is quite important that those who
really can't wear one are the only people who do not.