What would you say are the major qualities that make a person's actions/ behaviours abusive and the difference between the ones who do so intentionally and those who do so in ignorance of how destructive they are being? Big ask, I know, but I'm curious about what signs tip you off when it comes to complete strangers like the families you've encountered.
What makes behaviour abusive is if that behaviour aims to benefit the abuser in some way, at the cost of the abused. We call screaming at someone when they did something wrong "abusive" because the aim was to scare the abused into submission, to acknowledge the abuser's "power." Abuse is aggressive, though that aggression may sometimes be covert. The biggest factor though is that abuse has a negative impact on, a cost to, the person being abused. Whether that is the integrity of their self-image (in the form of humiliating them), or their feelings of safety (threatening them), their agency (manipulating them) or otherwise.
The thing is it doesn't matter if it's intentional or not; there's no real difference. You can absolutely be abusive without meaning to be--and this is actually the case about half of the time. My father, honestly--swear to God--never meant to be abusive. But it was what he knew, and what he could do with as little control over his emotions and insecurities as he had. But it still affected me and hurt me and left me with scars just the same. The difference is whether or not the abusive person will own up to it, when confronted with it.
Please note that I am hypersensitive due to my background. IRL, I'm not terrific at social cues, but I watch gesture, eye movement, body language, tone, wording, all of it. But it's not usually just one or two things that tip me off. It's typically a pattern. With most families I let them be, but when I start hearing or seeing certain things, I'll watch more carefully, and if I start seeing more of the signs, then I start getting more worried. I'm particularly wary of how parents will treat young children, because it's more apparent whether or not things are okay at home. It's easier to hide abuse with older children.
If you remember my post about trolls a little while ago, the biggest thing abusers need is power and control. Ad nauseum. This is kind of the biggest tip-off, and it'll usually come in the form of perfectionism and and kind of extreme demands from the parents. For example, I've seen a parent ask their child, in this absolutely nasty tone, "Hey, I asked you a question." They weren't loud. But their tone was a threat. They asked a question, how dare the child hesitate. Who cares if the child is three and only just barely grasps what their fingers do!
Often they'll order for their children, though it's apparent the child--even being like thirteen--really would like to do it themselves, they'll answer questions for the child when I very pointedly asked the child and they are clearly capable of answering on their own, they'll interject as the child is talking. If a child is young and kind of rambunctious, they act as if the child is a burden. "Ugh, can you take them already, god." Not in the exasperated, "I've been dealing with this all day" tone, but a tone more akin to a dog pissing on their lap. I've seen adults say to toddlers, "'Ey, can you knock that off? This's why I've already taken aspirin." Another tip off is, if the kid embarrasses them, do they get angry about it.
A big tip-off is, when a single parent is taking children out, does one of the children act like the "adult"? The second parent, almost. Because most often in abusive families, a child will become the parent's "babysitter" of sorts, having to shoulder the burden of the family and be the adult because the parents wouldn't be. (That was my role.)
Sometimes parents will humiliate their children in minor ways. When I ask, "Is everything all right over here?" I've had adults say, "Well it WAS all right until I found out my son didn't do his homework." Not in any kind of playful tone. Why do I need to know this? Because they want their kid to be embarrassed. This was the same family that had the babysitter child.
The biggest tip-off is, "Are they treating them like children, or like stupid adults?"
With children themselves, other than the babysitter child, you can sometimes spot tip-offs like chronically needing attention, sometimes they are absolutely austere and silent while the adult seems fine--though stern with their children. Sometimes those really bratty children are bratty because they have the strength to fight back against their parents who are being awful to them, and that's the only way to get them to back off.
With children, I'm looking for, "are they enthusiastically happy, or happy-but-walking-on-eggshells."
A lot of it is nuance and patterns though. Some of the things I watch for, if it happens once, or is a single item, you can kinda let that slide. Maybe they're havin' a bad day. But if there's a pattern being established that one or both of the parents need extreme control, or HAVE to maintain their authority, then you can almost bet that away from the restaurant, where they're on "good behaviour," it's gonna be worse at home.
I apologize if any of this is incoherent, it's two in the morning and I've written mostly off-the-cuff.