It seems to me that we have our own way of doing things. What we all were happy with as young mums is pretty much what we do as older people. I am another who 40 years ago hated people touching my children. I am still outraged by the assumption that it's ok it I'm afraid - however well meant, so I just don't do it.
To those who have rescued children from impending danger, I feel this is a different case! Thank you to the man who rescued my daughter from a road once when my child escaped from our (enclosed) back garden.
I was delighted as a young mum if a stranger played "peeping" games, and smiled at my babies and toddlers and was more than happy to engage with strangers with and about my infants on a friendly level.
Touch is something else.
Like some other posters I never touch other peoples children though I do often smile at them, wave at them, wiggle my fingers etc. I confine talking to them to a friendly hello. I sometimes talk to the adult about the infant "she's looking very happy today" for example, which I feel is communication without any presumptions.
I am not, nor ever was, particularly bothered about germs (however would not want that dirty coin in a baby's mouth - or someone's fingers!). I am bothered about the Herpes virus though, which can be devastating for infants and adults alike, (my father had shingles). My grandchildren have plenty of cuddles and kisses - but only when they want them. I never forced or expected my children to kiss people so don't expect my grandchildren to.