Hi, I'm sorry that my reply bummed you out. I certainly can see why you were deflated and I'm sorry that you were.
I do assume you're a good mom because your daughter trusts you and is expressive of herself. The things you cited as feeling proud of (about her, in the OP) are things I'd have been proud of (hearing from my child), and I'd have been proud of myself or reassured about myself, that that interchange could happen. It's a testament to what is intact in your little girl!
I didn't mean to suggest that you were mean in this exchange (I realize you didn't say you'd taken that from my message, just that you'd assessed that day as not mean), and I can understand feeling like it was a good parenting moment because, honestly, I didn't think it was a "bad" parenting moment!
To be clear, I don't think her capability to understand depends on you being a better mom or "doing better." I simply meant my guess is that she is capable (and yes, that is probably so because you are a good mom & she has had the space), and that in the moment what you were hearing from her probably was not so much lack of understanding as it was (also purely my guess & my perspective, and also my projection from my own life & circumstances and my kids & their reactions/signals) her being stuck in defending her validity.
Your child seems (it seems obvious, to me) not to have a lot of baggage because she didn't really escalate anything or make major protests, and she did express her feelings. This all speaks to a lack of defensive baggage. She didn't seem to need to attack or argue or engage in defensive protests....she just had her feelings. So I would not assume that you are a routinely negating/invalidating mom!
I'm not a routinely negating mom, either. But there are times (and it's not always a matter of "losing it" or being negatively reactive) when I miss the connection part, even though I don't handle myself poorly or messily. There are times & also specific areas areas in which it's harder for me to respond with my child's validity firmly in mind, even though I do have a habit of orienting myself that way. (When it involves a physical violation of someone else, that often is harder for me, though having twins made it become more routine/automatic out of necessity, because I couldn't allow myself to habitually think of one as an "aggressor" and one as a "victim," so I had to sprint up that learning curve to really being able to orient myself to the validity of any person, even if they were violating someone else, even deliberately so---being able to go to the needs and feelings even in that situation was important to me once both toddlers were "mine.") Still, there are times when I'm calm, validating (in terms of accepting their feelings and being willing to stay with them & support them through those feelings), and principled, but I still miss that I could have connected before correcting, and that some of those "feelings" are a direct result of me in the interaction.
Anyway, what I noticed from your description in the post was that you were open & curious with your daughter, and after she explained her upset, your response was to explain your action. (How you had to do it because she had hit the baby, or she hadn't been safe with the toy.) The focus was on why you took the toy away, and whether or not she understood that.
When I suggested she was stuck defending her validity, I wasn't assuming that you had invalidated her by chiding her for her feelings, or being impatient or disapproving of her upset, or assuming the worst about her intentions with the toy/accusing her of intending to hurt her sister. I simply noted that your focus was on explaining the reasons for your action in taking away the toy, which is establishing your validity. This is not harsh or cruel (and your child certainly didn't respond in any way that would suggest that you were being dismissive or pressuring), but explaining is about clarifying and persuading. It's an appeal. When the focus is on explaining how an action was reasonable and valid, it's suggesting why the other person "shouldn't" be upset about it (which is why it's experienced as invalidating.)
I agree that it sounded like you gave space for her feelings, and I can see why you didn't think of yourself as "invalidating." It is so easy to slip into being irritated by crying, and it sounds like you didn't. Being present with and allowing feelings as valid IS validating in itself. I simply was pointing to the invalidation (by omission, really?) of the explanation, the exchange that was repeated a few times. Not meaning to suggest an overall "spirit" of negation or invalidation (in which case it is less likely your daughter would be as expressive as she is, or else she'd be lots more combative, accusing or defensive in her expressiveness.) And not meaning to suggest that you did something "not good." Just that this could account for her getting stuck.
The thing I pointed out (about myself) above is kind of what I am suggesting: there are times when I'm validating (in terms of accepting their feelings and being willing to stay with them & support them through those feelings), but I still miss that I could have connected, or reflected them (rather than explaining the limit), and that some of those "feelings" are a direct result of me in the interaction.