Can we deduce from the fact that we recite after the reading of the book of Esther on Purim, “and Charvonah, too, be remembered for good" which is the opinion that seems to be getting approval?
I believe we can. But I will first try to be fair to the opinions that do not agree with my conclusions.
Those that hold that Charvonah is Eliyahu, will have to say like Aruch Hashulchan [Hilchot Megilla, Siman 690, halacha 22]
that the mere fact that Eliyahu chose to impersonate Charvonah gives him enough merit, for us to say ,"and Charvonah, too, be remembered for good".
On the other end of the spectrum, Muman613 brought in this discussion, some rabbinic opinion that holds that even though Charvonah was part of the evil plot, he deserves some credit from us for changing sides at a key moment, even if his motivation was for the wrong reason.
I however, disagree for several reasons.
Reason 1], the wording ,"and Charvonah, too, be remembered for good", most closely fits the third opinion which I brought in the Yalkut Shimoni quote above, which holds that Charvonah was a Gentile, official, who was not connected to the plot to hang Mordechai.
Reason 2] If Eliyahu was Charvonah, why is he not mentioned at all explicitly in our prayer of thanks.
Reason 3] A parallel passage to the Yerushalmi, which is our main source for the prayer of thanks after reading the book of Esther is in tractate Sofrim chapter 14.
There it says: "Afterwards one extols the righteous, Blessed be Mordechai, Blessed be Esther, and blessed be Israel. Rav states, one has to say Accursed be Haman and Accursed be his sons. Rabbi Pinchas states, and one has to say Charvonah, may he be remembered for good".
In this source, it is Rabbi Pinchas not Rav, who demands that
Charvonah, may he be remembered for good (although it is quite possible that both are in agreement on the issue, and so some places one of them is given the credit and in other places the other Rabbi is given the credit).
In this source, the clear implication is that Charvonah is someone outside of the nation of Israel, thus excluding Eliyahu.
A substantial number of prominent Rabbis, also had the text of the Yerushalmi saying a statement similar to that of tractate Sofrim chapter 14, such as, Tosafot Ha-Rosh to Megilla page 7, Tur, and Shulchan Aruch to O.C. chapter 690. However, they use different terms to stand for the good group, Israel, and they also add a bad group to the list of those that should be cursed, . However, what is common to all these statements, is that Charvonah is someone in the gray area between good and bad, who we have to be told explicitly that it is a requirement to remember him for good.
Reason 4) If an Israeli spy impersonated an Iranian Radical Islamic Terrorist, in order to bring the downfall of the modern Iranian Hitler, Mahmoud Ahmadinejad, I would feel no obligation to remember the true Iranian Radical Islamic Terrorist for Good. I see no reason, to remember Charvonah for good, just because Eliyahu might have impersonated him.
Reason 5) Similarly, I think it is going overboard to praise some Big Anti-Semite who plans to kill Jews, simply, because he betrays his fellow Anti-Semite, when he sees that it is politically dangerous for him to continue on his current path. So for example, when the new Iraqi government executed, Sadaam Hussein, for their own political reasons not connected to wanting to help the Jews, I see no Rabbi that demanded that we give the Iraqis any special praise for their action. So too, I don't think the rabbis would demand we remember Charvonah for good, if he was an evil man, who was just a clever political opportunist.
Reason 6] There are a number of wicked people in the Tanach, who had political or economic reasons to nevertheless help the nation of Israel. Just as those political opportunists aren't granted any special praise, I don't see why Charvona would be singled out for praise more than the other political opportunists in the Tanach .That is to say, if we indeed were to accept the view that Charvonah was an Anti-Semite, who betrayed his friend, Haman just because the political winds were shifting,
Reason 7] Talmud Bavli, Tractate Avoda Zara 2b implies that Gentiles don't get credit if they do things that benefit the nation of Israel, when they only had the intention when doing those activities of helping themselves with their physical needs and desires and did not intend at all to help Israel. Although if you wish to quibble with me, you could argue on this point, that although they don't get big credit for these type of actions, maybe they get minor credit.
Regarding this point, one might contend, revolved the famous story of Rabbi Shimon Bar Yochai, Rabbi Yehuda and Rabbi Yosi. Where Rabbi Yehuda wanted to praise the Romans for their accomplishments. Rabbi Yosi remained silent (and was punished for his mere silence by the Romans who exiled the rabbi from his city) and Rabbi Shimon Bar Yochai said they do not deserve any credit at all, because all their accomplishments, they do for their own physical needs and desires. And in the end Rabbi Shimon Bar Yochai had to hide with his son for many years in a cave to avoid execution by the angry Romans.
And even if one wants to agree with Rabbi Yehuda's viewpoint, even he probably would not go so far, as to institute a public prayer of thanks, to wicked Anti-Semites who betray their companions, because if that were true, we would even have to add the King of Persia, Achashverosh to the list of those that get praise, and it is well known that we do not do so.