I am 26 years old and look considerably younger, think 16-18, and if I had a pound for every conversation Ive had about how young I am I would retire a happy lady.
Now I understand I look young, I accept that even now I will get ID'd for everything (even scratch cards!) BUT when i show you my ID i dont want to have to then stand there for actual long minutes whilst you tell me what I already know!
Yes I dont look my age. Yes I have been told that. Yes I dont look old enough to have a baby, run a house, do a weekly shop etc. And NO I will not be happy about it when Im 50!
I think random comments can be forgiven to an extent but from people who you have showed an ID to its just plain rude. It would be like a slimming world instructor raving to class about how you are the fattest lass yet! But still random comments, probably not welcome when people are doing ordinary things like standing at a bus stop or doing the weekly shop.
So in summary, i think any comment about how someone looks TOO anything (old, young, fat, thin etc.) is just rude and although you may think you are being nice you may infact be rubbing someones biggest insecurity in their face.