Who are "ha'Charedim El Devaro"?
Bava Metzi'a 33b: They are Chachamim.
Rashi: They are Tzadikim who rush with zeal to come close to His words.
Malbim: They are truly zealous for His word; they do not bring Korbanos to boast, like the pretenders.
Who are "Acheichem"?
Bava Metzi'a 33b: They are people who learn only oral Torah.
Rashi #1: They are Yisrael sinners mentioned above.
Rashi #2 (according to Kli Paz' text): They are Bnei Esav.
Malbim: The pretenders act like your brothers in Mitzvos, but really, they are Sone'eichem Menadeichem (refer to 66:5:4:5).
Who are "Sone'eichem"?
Bava Metzi'a 33b: They are people who only learn Mishnah (they are unqualified to decide Halachah, but do so anyway).
Who are "[Sone'eichem] Menadeichem"?
Bava Metzi'a 33b: They are ignoramuses (Chachamim shun them like Nidos).
Rashi #1: They say "Kerav Elecha Al Tigash Bi" (65:5).
Rashi #2 (according to Kli Paz' text): It says about them "Suru Tamei Kar'u Lamo" (Eichah 4:15).
Radak: They are those who distance you because you are zealous for Devar Hashem. They hate you and distance you.
Malbim: In their hearts they ambush true Yir'ei Hashem.
Why does it say "Lema'an Shmi Yichbad Hashem"?
Rashi: Hashem is honored via our grandeur, that we are closer to Him than you are.
Radak: They say so - He is heavy on us with His Mitzvos that He commanded us. This is like "v'Lo Nichbad Alecha" (Shmuel II, 13:25). They say this on behalf of Hashem.
Malbim: They say that their bringing Korbanos publicly honors Hashem.
Why does it say "v'Nireh v'Simchaschem"?
Bava Metzi'a 33b: We will all rejoice.
Radak #1: Hashem will be seen and revealed in your Simchah that you will have in His salvation, and they will be ashamed.
Radak #2: This is said corresponding to ha'Charedim El Devar Hashem. We will see your Simchah - the reward of the Nefashos, or because they will be in Techiyas ha'Mesim in Yemos ha'Mashi'ach.
Radak #3: This is said corresponding to ha'Charedim El Devar Hashem who returned from Galus.
Malbim: The Navi responds, at the time of your Simchah (of true Yir'ei Hashem), the Emes will be seen - they (the pretenders) will be ashamed.
Who will be ashamed?
Bava Metzi'a 33b: Nochrim will be embarrassed, but Yisrael will rejoice.
Rashi: The Navi says, it is not like you say. We will see your Simchah, and they will be ashamed.
Malbim: The pretenders, for they will see that Hashem does not desire flattery, only true service of the heart.