I would really like to hear what this yelling was about. Perspective is a hell of a thing.
There are some exceptionally capable people who simply cannot work together on the same idea/problem in my experience. This doesn't necessarily mean that one or the other is inherently bad.
Healthy? The linked post reads as very snide. Ben starts with claims that Chris isn't viewing his comments in context as being opinion. Rather than move on at that point, he turns around and decides to nitpick one of Chris' statements, characterizes it as hyperbolic and extreme (The extremely hyperbolic phrase in question was "betray a lot of expectations and introduce a lot of bugs." Wow, such extreme hyperbole).
Ben then goes on to call another one of Chris' posts as representative of a part of a broader trend of "performative misunderstanding", basically calling Chris and others disingenuous.
He then dismisses Chris' concerns out of hand as "a possible but frankly implausible misinterpretation", and says that his behavior is a "real problem" that worsens the goodness of other proposals.
I'm not saying that either party here is in the right, or that the discussion as a whole is in Chris' favor, but I would say this thread is definitely not an example of healthy debate. You don't call your interlocutor disingenuous in healthy debate hyperbolically nitpick their posts as hyperbolic. That's not debate, it's squabbling.
This is not a normal forum conversation though. It influences binaries on billions of devices. Lattner wanted to push his own opinion and got (IMO) gently rejected. Fair enough.
Lattner's point was that high-level design considerations should be thoroughly discussed well before even finalizing the design, never mind the bikeshedding on syntax that takes up much of the thread. Swift's design discussions seem severely dysfunctional compared to how other languages do these things, e.g. Python's Enhancement Proposals, Java's Community processes or Rust's RFC's.
There's two sides to every story?