I suspect the downvotes are for a very simple reason: "Why not Rust?" comments are contributing next to nothing to the conversation. At this point, comments like this are tiresome and predictable.
What would be interesting are detailed separate posts such as what you mention about security exploits addressed and of course the stream of wonderful software that people are writing in Rust (and other languages as well for that matter). Bringing it up in relationship to Ladybird, which is an amazing accomplishment already, is incredibly petty and off-putting. The poster can do better and the community deserves better.
Unless I’m misreading, OP themselves didn’t actually say Rust at all. They just noted that Ladybird is written in an unsafe language.
I don’t read this as petty, it’s well noted by now that memory safe languages are increasingly recommended to avoid classes of errors.
You are correct about Rust not being mentioned explicitly, but I am yet to see a stream comments about memory safety coming out of say the Java, Python, Go, Haskell, etc. community. Then again, maybe I am wrong?
As for petty. "[B]uilding a new browser in 2024 using an unsafe language is such a facepalm it's hard to take the entire project seriously." sounds pretty darn petty and dismissive to me for a project that is making good progress. We desperately need diversity in terms of web browser implementations and "not taking seriously" a project which could very well become viable within the next few years solely based on their programming language of choice feels wrong to me (even as someone with next to no love for C++).