username: “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.”
I honestly think you are wrong. And I have never heard of any lubavicher who sleeps in a sukkah, or who has even tried to to see if he will fall asleep.
Which leads me to ask why, according to you, lubavichers don’t go to bed in the sukkah and see if they can fall asleep. I assure you that someone who doesn’t have insomnia will fall asleep eventually.
“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.”
That is not at all similar. (Disclosure: I don’t really know the extent of the issur of clapping on Shabbos, and I don’t know the heter for doing so by chassidim. So I’ll just take username’s explanation as is and deal with it as if it’s correct.) There is an issur to clap on Shabbos, and for some reason that was “ignored” to enhance the mitzvah of Shabbos. There is an issur to go to sleep outside the sukkah on Sukkos. Ignoring that issur does not enhance the mitzvah of sukkah, If anything it enhances one’s sleep outside the sukkah, which is an issur.
If it were a mitzvah to sleep during Sukkos, then you could say that sleeping outside the sukkah to enhance the mitzvah of sleeping is similar to clapping on Shabbos to enhance the Shabbos. But the mitzvah is sleeping IN the sukkah, and sleeping OUT of the sukkah can’t enhance that.