L'chovod Rav Kornfeld sh'lita,
Regarding the question of how the angel who killed the Tzeduki Kohen Gadol was permitted inside of the Kodesh ha'Kodashim, I believe an alternative answer (besides that of the Yerushalmi) could be given.
I once heard a p'shat on the posuk of "v'Chol Adam Lo Yiheyeh b'Ohel Mo'ed" (Vayikra 16:17) that the Kohen Gadol himself, after going through the week-long preparation prior to Yom Kippur, was elevated to the level of an angel! (Therefore there was literally no one on the relatively low level of "man" present at that time.)
According to this, there wouldn't be any problem at all with an angel going inside of the Kodesh ha'Kodashim at that time. Taking this one step further, perhaps that was partly the reason why this Tzeduki was killed, being that he obviously was not elevated and did not act properly.
The mere fact that he was killed, and particularly as he exited, was in itself proof that his avodah was done incorrectly. If it was properly performed, why then would he have been killed at that precise moment, after he had just completed his avodah, thereby bringing about atonement?
I would greatly appreciate your comments on this.
Kol tuv.
Saying that the Kohen Gadol had the status of a Malach and Malachim are permitted into the Heichal needs support, because we do not find any source that argues with the Toras Kohanim's interpretation of the verse (Vayikra 16:17) that an angel may not enter the Heichal.
Regarding the Midrash that you cite, that the Kohen Gadol was not considered an "Adam," it seems that the Midrash means that he was elevated above the status of a Malach, for an Adam is greater than a Malach when he is elevated, for he has the power of free choice and he chooses to serve his Creator. (It could be suggested, "Lulei d'Mistafina," that the Kavod of the Shechinah itself enwrapped the Kohen Gadol, as the TOSFOS YESHANIM suggests in answer to a similar question in Yoma 39b, DH Nichnas.)
What you write regarding the Kohen Gadol being killed because he was not elevated, that is an excellent suggestion, and the same for the suggestion that his death shows that his Avodah was not done properly (that part is already similar to the approach of the Meshech Chachmah that we cited).
Be well, Mordecai
I found the Midrash to which you are referring -- it is at the end of ch. 21 of Vayikra Raba. Your question is compounded, because that very Midrash begins by quoting the story of SHimon ha'Tzaddik and the "old man of grey hairs" that entered the Kodesh ha'Kodashim with him, and concludes, like the Yerushalmi, that the old man represented the Ribono Shel Olam Himself -- since it could not have been an angel, for angels are not allowed in during the offering of the Ketores. Yet the Midrash then states that the Kohen Gadol himself was only permitted because he was not a person, but "his face shone as flames, as it says (regarding Pinchas) "for he is an angel of Hash-m Tzevakos."
What does that accomplish -- angels are not allowed in, as the Midrash stated immediately above! (The commentaries have a very hard time with this. The MATNOS KEHUNAH and MAHARIF claim that the beginning and end of the Midrash are representing two differing opinions as to whether an angel was allowed in, as you said. But this answer seems very forced.)
My earlier answers that the Kohen Gadol, who was a person, was on a higher level than an angel, or that the Kavod of the Shechinah rested on him, are not so appropriate in light of the Midrash's quote that justifies the Kohen Gadol's presence because Pinchas was "like an angel" (unless we differentiate between "an angel" and "an angel of Hash-m Tzevakos", which is a higher level of angel and is permitted in the Mikdash during the Ketores, see Rambam Yesodei ha'Torah 2:7).
However, I think that the Midrash may be explained as follows: An inference (Diyuk) from a Pasuk does not apply to what is learned from another inference in the Pasuk, but rather only to what is stated in the Pasuk itself.
That is, in this case the Midrash is discussing two Diyukim from this Pasuk: (1) The Pasuk says "Adam" should not be in the Heichal, rather than "Ish," the usual work for person. From this it learns "even those of whom it was said, "u'Peneihem Pnei Adam" (i.e. angels) are not allowed in the Heichal. (2) The verse adds, "v'Chol Adam" should not be in the Heichal, seemingly including anyone, even the Kohen Gadol himself. From this we learn that the Kohen Gadol was like an angel. The verse itself does not disallow angels in the Heichal, just the Diyuk. That Diyuk, though, does not apply to the angel that is the Kohen Gadol himself, since he obviously may be there. (He is only excluded from being there by the Diyuk of "v'Chol Adam," which only excludes him from being there as a person, but not as an angel.)
This seems to me to be the intent of the Midrash.
-Mordecai