So a bit earlier there was the comment, "Well 10 pages later, I still don't know what most people would do in those situations *sigh*" SOOO, here are a few examples ... But bear in mind I think the whole "please, thank you" issue is SO MINOR compared to a kid's overall respectfulness towards others.
I'm at a party (holiday, birthday, whatever) with my 3-year-old. She's given a gift. She tears it open with glee and then looks around for the next exciting thing (no "thank you" given). I'd take the gift, address the giver, and thank them. Probably, if she heard me, DD would chime in with "Tank you!" If not, no biggie. When we are preparing to leave, I might say privately to her "Did you have fun? Yeah? Auntie was so nice to us today. Let's remember to say thank you to her when we say goodbye."
I'm at a party with my 6-year-old. She's given a gift she's in ecstacy over - too in love with it to look up and say "thanks". I address the giver and I thank them, pointing out how pleased DD is. When her initial joy has subsided a bit and I catch her eye, I might mouth the words "Thank you" or say "Come here a sec, sweetie," and quietly ask "Did you remember to say thanks to Auntie? It'll make her happy, I think."
Or ... she doesn't really like the gift ... puts it aside, no comment. I thank the giver, then as soon as I had a private moment with DD, say something like "I guess you didn't like auntie's gift, right? Why not? Well ... I understand you don't like it. Maybe we can change it, I don't know. But you know, you still need to say something to Auntie. She was trying to do something nice, right? Yeah. What do you think you'll say? ... That's nice, I think she'll like that, let's go talk to her." And I'd go with her, and if Auntie made a big deal of "So you didn't like the gift I got you!" I'd intervene, because a 6 year-old is not a diplomat, and try to nicely explain so that NEITHER auntie or DD gets hurt.
I'm at a party with my 8-year-old. She's given a gift... She opens the paper, looks at it, and loudly says "YUCK. This is so STUPID." I would stand up and immediately say, "DD, come in the kitchen with me. I want to talk to you." And I'd take her out of the situation. Shaming? Yes, probably, depending on the kid. But shame is a valuable emotion like others. I have felt ashamed of being mean, and I WANT my child to feel ashamed when they deliberately hurt someone's feelings. And at age 8 my child, if reasonably empathetic, is going to KNOW she just hurt auntie's feelings. In the kitchen I'd say how that was hurtful and rude, and ask if DD could think of a way to make the situation better. I wouldn't demand it but would make it clear the best thing to do would be an apology AND a thank-you for the thoughtfulness of buying a gift at all. At age 8 I am almost certain DD will want to do that.
Just a few examples of where I would use language to go "above and beyond" pure modelling. I do not feel that these are shaming to my child, except as I said possibly the last; I do not think ANY of these are belittling or damaging. In the last case, I think if all I do is model a nice polite "thank you" of my own to Auntie, I am reinforcing DD to feel any and every thing she does is fine, regardless of the feelings of others.
I'm not saying "this is what you should do with YOUR child" but rather what I'd do with my own, who I know.