I am an old fogey so bear that in mind as you read this. I am a great believer in, if possible, being formally introduced before making conversation.
Put another way, I think you have to know the person. Years ago, I worked at a firm where the secretaries all kept a supply of birthday cards for the 40-50 partners and staff. I have never been one for cards and certainly not birthday cards. Now, that may sound like I am a dour, boring, humorless old git. Nope. My humor is just very dry and very Scots. So, on my birthday one year, I got to my desk at the end of a long corridor and there was the usual pile of cards. One that I opened was from the receptionist. It was a sympathy card.