I am not sure how i would feel about my 16 year old going to a concert on her own but I think i would be ok if she was 17 and close to turning 18. I do think it depends on the child and how responsible they are. Only you know what your child is like. You could always buy a ticket and still go with them but sit a few rows back so they feel like they are going with just some friends.

I think it’s probably old enough depending on who they are seeing i.e. Taylor Swift would be fine, but maybe not Metallica. They are old enough, but it’s not just them you need to worry about, but the others attending too. You never know what unsavoury characters might also attend. There would need to be strict guidelines and maybe you drop off and pick up? Make sure there’s a group of them together too.

Oh yes, totally fine for them to go without parental supervision at that age. IN fact I would be concerned that I would embarrass my kids if I would supervise them when they go out with their friends at that age.
A lot of children at that age can drive a car even, so they may be able to go on their own accord or take public transport together as a group as friends.
It’s also good for their independance.

Definitely okay for them to go without parents. My first concert without parents was in grade 10 at 15. All I cared about was fan girling over my favourite artists. If you have trust between you and your child, I would say let them have this experience. And the standing area isn’t bad. If they are going to indie or rock gigs it isn’t going to be a hardcore mosh pit.
One of my favourite memories is my mum letting me wag school, driving my friend and I to a concert at 15. We were in the standing area and I got to meet 3 members of the band while another played.