I agree strongly with you refusing @hostilefork's invitation to say there's “no engineering seriousness” in Red.
Not because I think you needed to be diplomatic. Quite the opposite: your narrower accusation is substantially nastier because it's defensible.
Red plainly contains serious implementation engineering: compiler/toolchain, Red/System, GUI work, platform targets, etc. Saying otherwise gives an opponent an easy factual objection.
But:
is an accusation someone has to answer on the merits.
And examples such as break/return matter because, assuming the analysis in the thread is correct, they suggest something stronger than historical baggage. A design had an ambiguous communication channel and subsequently added functionality that depends upon the ambiguity instead of resolving it.
That's evidence about design methodology, not merely an old Carl Sassenrath mistake that Red inherited.
"a DSL substrate it doesn't deliver and hasn't in twenty-five years."
It has not even been around that long, so how can it state such thing? In about 10 years time, yes absolutely. The expected progress suggest the validity of the statement to be that.