Rashi writes (3) that white always appears lower than the skin. How can we understand "v'Amok Ein Mar'eha Min ha'Or"?
Ramban (3, according to Rashi): We can say that a Nega appears deeper than the skin when only white or yellow hairs appear in it, but not when there are black hairs. 1
Ramban (3): Se'es is an expression of height (Shevu'os 6b, Toras Kohanim), and it is white! We can say that it is higher than Baheres, which is whiter.
Seforno: It discusses when also the skin is more white than usual. Moshav Zekenim, Da'as Zekenim citing Maram - in a Gormani (Albino), who is even whiter than Baheres 2 , it does not appear deeper (Nega'im 2:1). 3 Why did Rashi leave this difficult?
Rashbam: It discusses where the Nega is less white than any of the four Mar'os Nega'im that render him a Metzora. 4
Ra'avad (Hilchos Tum'as Tzara'as 1:6): Only Baheres is deeper than the skin. Targum Yonasan: It discusses where the Nega is white like lime (the Toldah of Baheres) but not like the Baheres itself. 5
Riva, Hadar Zekenim, Da'as Zekenim: Regarding Shechin (verse 20), Toras Kohanim includes what is 'Shavah l'Gavoha', i.e. the Nega is not recessed into the skin. Also here, we include what is even with the skin. 6
Moshav Zekenim citing Maharam: "Ein Mar'eha Min ha'Or" starts a new matter. The verse means, the Baheres is Amuk; its [deep] appearance is [due to the whiteness, and] not Min (from, i.e. due to) the skin. The Ta'amim support this. 7
Chasdei David (on Tosefta 1:6, based on Ra'avad in Sifra): A Baheres is sometimes deeper, and sometimes not deeper. Se'es is always higher.
Maharam Shik (YD 400): The prefix Vov (v'Amok) alludes to Baheres and another [small] Nega that join to a Shi'ur. This explains why the verse begins "v'Im Baheres", even though also the previous verse discussed Baheres.
Because then, it does not appear lower than the skin - just like a dark spot in an area on which the sun is shining. (According to this, if some hairs turned white, and black hairs remain, he is not Tamei. Rashi connotes that if two hairs turned white, he is Tamei! - PF).
Da'as Zekenim: How can we find a person whiter than snow?!
The Mishnah only discusses whether we view a Nega against his skin, or against that of an average person. R. Shimshon there says that a bright Baheres looks weak on him. (PF) Maharam Shik (YD 400) - how can we answer for R. Yehudah, without says that a Gormani is judged based on his skin? If so, he is Tahor!
However, it is not then clear why the person needs Hesger! (EC)
Maharam Shik (YD 400): The verse discusses a Baheres! Toras Kohanim includes Se'es; the verse means, when Se'es is next to Baheres, it is not deeper. Or, the prefix Vov (v'Amok) means 'or'; if it is a Nega other than Baheres, which is not deeper
What does it mean "v'Hisgir ha'Kohen Es ha'Nega"?
Rashi: The Kohen confines him in his house and does not see the Nega for a week. Then, the Simanim will determine [his status]. 1
Refer to 13:4:151:2,3.
Rashi writes that the Kohen confines him in his house. In all of Maseches Nega'im, we do not find confinement in a house! Also, it says v'Hisgir
Ha'Kesav veha'Kabalah: Rashi does not mean that the Kohen locks the door. He did not mention this. Nega'im 1:12 shows that he may enter the Beis ha'Keneses! Even Bayis ha'Menuga need not be locked! Rather, he closes the door, lest it be open to passersby.
Hadar Zekenim: The Kohen does not see the Nega for a week. Then, he will be able to judge if it expanded. If he saw it every day, he would not notice the difference between one day and the next.
Moshav Zekenim (4): A Tosefta teaches that sometimes we are Masgir two Nega'im in a person, and sometimes only one of them! A Tosefta teaches that Hesger is with ink, or red dye. (Tosefta (4:3) discusses being Masgir only one; I did not find the other Toseftos that he cites - PF). Also Minchas Chinuch (Mitzvah 19, 10) cites the Tur citing the Rosh, to say that Hesger is with red dye.
Ha'Kesav veha'Kabalah: This is difficult. We say that if a Kohen saw a Nega and died, another Kohen cannot tell whether or not it spread!
Da'as Zekenim, Hadar Zekenim - we cannot say that he marks around the Nega, for the Metzora could erase it and make a new mark! Only regarding Nega'im of the head, he marks it through shaving hairs around it; this cannot be forged.
Abaye expounds "Baheres Levanah Hi" - nothing is whiter than it. Why is this needed? We should know this already, for it is more Amuk than Sees!
Moshav Zekenim: One might have erred to think that Se'es is an expression of whiteness, for it says "Se'es Levanah" (verse 10), or an expression of attributes, like "Yeser Se'es v'Yeser Az" (Bereishis 49:3), which refers to the attributes of Bechorah and Kehunah.