Megillas Sesarim says Esther was arguing here that her not being summoned in the last thirty days was indicative of the fact that she soon would have to be requested.
R’ Yaakov of Dubno gives the opposite answer – since Achashverosh had not called her in thirty days, Esther feared that he had lost interest in her.
Kisei Shlomo writes that Esther realized that the Jews’ salvation would really not come from her, but through their own teshuvah. She therefore picked the large number of days to buy time for the Jews to repent on their own.
The Maharal quotes from the Talmud (Brachos 58b) that a person who is reunited with a friend after thirty days says the blessing of Shechechiyanu. The Maharal explains that the reason for this is the intense joy brought about by the cessation of the absence. In other words, Esther emphasized that she had not been summoned for thirty days to clarify that when Achashverosh will actually summon her after so long a separation, his emotional state will be far more amenable to her suggestions.
According to Rav Yitzchak Hutner, this entire conversation justifies the custom of drinking on Purim ad d’lo yada, up to the point that one does not know the distinction between “blessed is Mordechai” and “cursed in Haman” (Talmud, Megillah 7b). He explains that, during the rest of the year, we are warned against digging deep into the secrets of the world, like the material from which the Earth was made, the symbolic meaning of Yechezkiel’s vision of H-Shem’s chariot and retinue, etc. On Purim, however, the point of drinking is to break down our inhibitions, open our minds, and reach levels of intellectual understanding to which we are not usually privy. On Purim, too, we are able to enter the courtyard of the King, and He will allow us to comprehend that which we were otherwise not invited to understand.
The Maharsha says that, as we shall see in the next answer, the party was meant to endear Achashverosh to Esther specifically for her to divulge her lineage. It was therefore named after her. The Me’am Loez reminds us that “Esther” also means “hidden,” and this feast was thus meant with the express purpose of her revealing her secret identity.
Also, the above-mentioned concern for the poor also makes this uniquely “Esther’s” party.
The Ben Ish Chai adds that this party demonstrated to the people conclusively that the icons of Vashti were down, and the king’s heart belonged wholly to Esther.
Rav Chadidah says this party was made by Achashverosh for Esther, as opposed to Vashti’s party, that she made for herself (1:9). Rav Chadidah points out that this proves a great affection the king had for his new bride.
The Malbim contends that Esther, besides possessing health and beauty, also had great character because of her distinguished father. We know that he was a great man because it says in the Talmud (hinted at in Megillah 10b) that all prophets must have good genealogy.
Another reason for her father to be mentioned here comes from the Maharal. He quotes the verse in the Torah (Bireishis 2:24) that says a man who finds his intended should cling to her. Maharal continues that a woman, too, clings to her husband after marriage. Therefore, Esther was connected to Mordechai up until this point, and will now have to cling to her new “husband,” Achashverosh.
The Talmud (Megillah 13b) says that Esther’s ancestors Rachel, Benyamin, and Shaul were all able to keep secrets. This characteristic was passed down through Avichayil to Esther. Rav Chaim Kanievsky says this verse emphasizes this genetic link to secrecy. This is why Esther’s father was not mentioned earlier when her secrecy was first mentioned (2:10 above), because there, she was commanded to be secretive by Mordechai, and this verse is attesting to her innate ability to do so for this long period of time.
According to Targum Sheini, Mordechai was concerned that the king would become upset with Esther at some point, and take his anger out on her people. This is similar to what actually happens when Haman becomes angry with one Jew, Mordechai, and decides to exterminate his entire people as a consequence (see below 3:6).
The Ibn Ezra quotes commentators critical of Mordechai for this order, saying his selfish intent was for Esther to not be chosen by Achashverosh, so that she could return to being Mordechai’s wife. He rejects these opinions, and comments that Esther’s keeping this secret allowed her to stay Jewish because the king would have used violence in an attempt to force Esther to convert had he known her background.
Rabbi Eliezer of Worms writes that Mordechai knew that Esther’s very presence in the harem of the king meant that she was placed there for a reason. After all, wherever we are in life, H-Shem wants us there for a reason, though we often do not readily know what it is.
Rav Moshe Meir Weiss adds that even if Esther did not understand the reason for her secrecy, or even if she disagreed, this verse is a praise to her for listening to the words of Mordechai, the Gadol HaDor (greatest rabbi of her generation). When we trust the Sages, things go well for us.