I think you are correct about Rust being substantially different from C, but that's a nasty way of saying it ("you know absolutely nothing about..."). Is it really necessary to speak that way?
Moreover, it was mean-spirited. Probably because they were reacting to the second part of dmitrygr's quote.
Consider the Stylo project in Firefox, for example. Yes, Mozilla could have done the parallelization in C++ instead of Rust. They even tried! Twice! But it failed both times. That doesn't mean that it's impossible.
In my experience, this is what people mean when they say things like this.
Look, I'm a big fan of Rust - I want to see it succeed. I go to Rust meetups in my city, I've advocated for it's adoption in my company, yadda yadda. But I don't these vague half-truths are good for the language or the community. In fact, I think they'll be harmful to the community over time as the language will fail to live up to expectations. When I started programming, Java was in the position of Rust. It was being given so many vague platitudes that it experienced push back a few years later as developers realized it didn't fix all their problems.
I don't mean for this post to be mean or condescending. Tone is hard to transmit over the internet.
That is, I 100% agree with your comment, but I don’t see it happening in this thread.