In what situation would you...

[Fujiko]

...verbally discipline someone else's child?

Specifically, a stranger's child in a public setting?

[Fujiko]

For me, I found that I did it, automatically, when we were at a playground and my dd was standing with another toddler on a 2-3 foot ledge and the other toddler started pushing her. I panicked and said, "Please don't push!!" before I could get to her and grab her. It's not that I found the other child's behavior inappropriately BAD, they're just toddlers. I just freaked out because I thought she was going to fall. The mom was 15 feet away talking to another mom and approached after this quick incident, saying something like, "It's hard to be a kid, huh?" I just smiled and led my daughter a little further away, to give them some space. I don't know if I committed a breech of mommy etiquette.

[rachelsmama]

If one kid is about to hurt another, or being really mean, or if a kid is obviously about to get hurt. I would just say/do enough to stop the situation though, and possibly give a brief explanation if the kid looks confused, but I wouldn't do any lecturing or punishing, or anything like that.

ETA: of course if the appropriate parents are there I would wait for them to deal with it.

[lara1828]

If I see a child throwing sand, I will tell them "No throwing sand!" (after waiting a beat to let a parent intervene). This is a universal rule at any playground I"ve ever been to and is a basic safety issue.

A couple times I've told older children (>5) to watch out for littler kids when they are tearing around on the playground equipment. Again, a basic safety issue.

A couple of times unsupervised kids have tried to "own" a piece of playground equipment and told my kids they can't use it. I reminded them that the playground equipment is to share and tell them they need to move (or whatever). (If a parent is present and allowing their child to do this, I take the passive-agressive approach and loudly tell my child let's go do something else since this child isn't sharing/taking turns)

No kid (or parent) has ever given me attitude about these things.

[earthmama369]

If the other parent is busy or out of range, I'll step in if a child is about to get hurt, hurt someone else, destroy property, or is snatching/grabbing/pushing/ganging up (basically, acting unfairly). As long as everyone's having fun and being safe, it's cool.

[mbhf]

If they are hurting another child and no one else is doing anything about it, or if they are hurting my child.

If they are taking something from my child (that belongs to us) and their parents don't step in.

[One_Girl]

If my child is affected negatively by something they are doing or saying to her then I would redirect a stranger's child and help my child move to a different activity away from that child.

[Seie]

I dont mind speaking out to kids pretty much anywhere if behaviour is going on that I would deal with were it my own kids (if the parent is not right there doing it that is).

I expect others to enforce their own boundaries when dealing with my kids. For instance if people come to visit usually my kids will be all over them. I tell the guests that they are free to say "No" and then I expect people to enforce their own personal boundaries. If that makes sense. If one of my kids keep climing a visitor I will tell the visitor to tell my kid when its not ok anymore. There is no way I can know when someone else thinks its ok for my kids to want to play - only they themselfes can know that.
Just as when I am interacting with other kids, I will enforce my own boundaries and encourage my kids to do the same - and help them when they dont succeed obviously.
Also if my kid is rough towards another kid I will ofcourse tell my kid its not ok, then I will tell the other child that its ok to say "dont push me I dont like it"

If other parents have a problem with me talking with/to their kids - well - its called social interaction and its what happens when you get out among other people. As long as the communication is non-violent and fits the context I dont see the problem.