Any Lubavicher I’ve asked.
Do you?
I think I’ve pointed this out before, but if I haven’t, I’ll say it now. If a person can sleep soundly in a Sukkah, he absolutely has a Chiyuv to sleep in a Sukkah. And I’m almost positive that the Rebbe said the same in that Sicha.
You responded to RSo’s question without addressing his point. He asked how the p’tur can come from the mitzvah itself
Another similar Sevarah is the clapping on Shabbos. How can you use Simchas Shabbos as a source to permit an Issur Derabanan on Shabbos? And you can ask rso’s question on him too, by the way. Did no one before the Baal Shem Tov have true Simchas Shabbos?
But let me ask you like this. A person has a mania that the Sukkah’s caving in on him. Would he be Chayav in Sukkah?
And as to your question of why we’d want to be lenient here, it’s a Kullah that brings to a Chumrah. Just like the early Chassidim weren’t makpid on Zman Tefilla to have better Kavanah, early Chassidim weren’t makpid on clapping on Shabbos in order to have a stronger Shabbos, so too early Chabad Chassidim (as well as some others) didn’t sleep in a Sukkah in order for them to have a stronger “feel” for a Sukkah. So while I wouldn’t start such a minhag, and the Rebbe wouldn’t start such a minhag, the Mitteler Rebbe (and since you asked me why I am lenient here, I, personally, think that this quote was said by the Mitteler Rebbe) was early enough to institute such customs.