Isn’t a change to the code that incorporates your suggestions enough acknowledgment? Presumably the code change would be required to get your approval?

Of course! I didn't state it explicitly, but what I was referring to were comments that went completely unacknowledged in any way, be it explicit or implicit. No changes. No reaction. No "resolve comment". Radio silence.

As mentioned, I've experienced it too many times where not addressing a question/concern I put on the pull request led to outages that could have been avoided. I think it's typically a certain personality. It's not a common occurrence, but I have experienced it.