Why does the Torah switch to the plural ("ha'Nefashos ha'Osos")?
Rashi: To incorporate both the man and the woman in the Chiyuv Kares. 1
What are the connotations of "Venichr'su ha'Nefashos ha'Osos ? "?
Refer to 17:9:1:1 & 2.
Seeing as the Torah mentions Kareis by each off the Arayos in Kedoshim, why does it need to compare them here in connection with Karei?
Yevamos, 54b: To teach us that, like Nidah, Ha'ara'ah by all the Arayos is subject to Kareis. 1
Why does the Torah insert the words "ha'Nefashos ha'Osos"?
Sifra: To preclude kissing and hugging the Arayos from Kares. 1
Why does the Torah switch from Galus to Kares?
Oznayim la'Torah: Because, whereas the previous Pesukim were referring to the Tzibur sinning (and the Tzibur is not subject to Kares), the current Pasuk is referring to individuals.
Why is it that, out of the thirty-six Kerisos in the Torah, many of them pertain to the Parshah of Arayos sixteen of which are also subject to Misas Beis Din, as opposed to Ma'achalos Asuros, which are not subject to (Kares or) Misah at all?
Ramban and Moshav Zekenim: Because the Torah considers Giluy Arayos particularly disgusting, 1 it issued harsher punishments to prevent it.
Ramban and Moshav Zekenim (both citing Rambam in Moreh Nevuchim): Because the Yeitzer ha'Ra for Giluy Arayos is so strong, it requires a powerful deterrent to counter it.
As we see in this Parshah and in many other places in Tanach. And that also explains why Chazal always place Giluy Arayos before murder, when they refer to 'Avodah-Zarah, Giluy Arayos and Sh'fichus Damim' (Ramban).