“NO-ONE will ever consider arguing with the Rebbe in halacha, even in cases where he’s demonstrably wrong (ie sukkah et al).”
You don’t need to agree with the Rebbes justification of a long standing Minhag Chabad. The Rebbe didn’t make up this Minhag, the Rebbe merely justified it Halachically. I highly doubt that you even read what the Rebbe says about it in the original Sicha, not some nonsense on “Chabad Talk” .
(And here I should point out, that all your references to this Chabad Talk forum are irrelevant. I had never even heard of this forum before, and it hasn’t been active in years, and a cursory look at it will show you that it was primarily used by clueless BTs)
Also, Chabad weren’t the only ones not to sleep in the Sukkah, neither did Belz before the war. In a shmuess between Rav Shterenbuch of Antverpenn and the Satmar Rebbe of KJ, the latter says: “In Dzhikov one did not sleep in the Sukkah. If somebody happened to doze off in the Sukkah he would be awakened, so that he not transgress… They would wake him by saying: “Nu, Sukkah…”
But of course, if they aren’t Lubavitch, their Minhag doesn’t bother anyone…
Our Minhag of not sleeping in the Sukkah dates back to the Alter Rebbe, and the Mitteler Rebbe instructed Chassidim not to sleep in the Sukkah. (Sefer HaSichos 5699).