An answer may lie with interpretations of the phrase רבנן...דמצייני כמלאכי השרת רבנן found in Nedarim 20a.
Furthermore, see Maharal, Nesivos Olam, Nesiv Haemes 3:3:
כי אין התורה בארץ רק שהאדם שיש בו התורה נחשב בשמים מצד התורה שהיא מן העליונים, ומפני כך אמרו בכל מקום (נדרים כ', ב') מאן מלאכי רבנן שבשביל התורה שיש עמהם אשר התורה היא מן השמים נחשבו רבנן ...
To quote Rav Shimon Shkop's take on that gemara (Chagigah 15b; translation mine, taken from "Widen Your Tent: Thoughts on Life, Integrity & Joy", ch. 1, available here, pp 71-73):
But to my mind it is worth knowing and
contemplating what our Sages said on
Chagigah 15b. How could Rabbi Meir
receive Torah from the mouth of Acheir
[the former ...
From the Talmud (Moed Katan 17a):
There was a certain Torah scholar who gained a bad reputation due to
rumors about his conduct. Rav Yehuda said: What should be done? To
excommunicate him is not an option. The Sages need him, as he is a
great Torah authority. Not to excommunicate him is also not an option,
as then the name of Heaven would be ...
In his diary entry for August 6th, 1754 R. Hayyim Joseph David Azulai describes meeting R. Jacob Joshua Falk:
ותכף הלכתי לקבל פני הרב בעל פני יהושע הנז' ומראהו כמראה מלאך האלדים
I went immediately 'to receive the countenance' of the Rabbi, the author of P'nei Yehoshua aforem. 'And his appearance is as the appearance of an angel of the L-rd'!
The prophet Zachariya (3,7), according to the Targums explanation, refers to angels as "those that stand by".
'Thus saith the LORD of hosts: If thou wilt walk in My ways, and if
thou wilt keep My charge, and wilt also judge My house, and wilt also
keep My courts, then I will give thee free access among these that
The accepted reason that ...