What are the connotations of the word "Anav"?
Why does the Torah mention Moshe's humility here?
Da'as Zekenim, Hadar Zekenim: This shows that he did not marry her due to haughtiness. 1
Ramban #1: To teach us that Hashem took Moshe's part precisely due to his humility, since Moshe would never retaliate, even if he knew that someone had said something offensive about him.
Ramban #2 (citing Ibn Ezra): Moshe would never seek to be superior to anybody else, nor would he flaunt his superior position to anybody else - certainly not to his siblings.
Why is "Anav" written Chaser (without a 'Yud')?
Rashi (in Sefer ha'Pardes): It can be read 'Anu'. In answer to their criticism that, on his own initiative, Moshe had separated from his wife and had negated the Mitzvah of 'P'ru u'Revu', Hashem challenged them 'Anu Bi!' Testify against Me, when did Moshe ever do anything against My wishes?
Da'as Zekenim: When you write out the letters Ayin (Ayin, Yud, Nun), Nun (Nun, Vov, Nun) and Vov (Vov Vov), the Gematriya is 248. This teaches that he was humble in all his limbs.
Rosh #1: Moshe omitted the Yud, for it was hard for him to write this about himself. Hashem said, you omitted a Yud from your honor
Why is Moshe praised for his humility?
Lev Eliyahu (Bereishis p.125): Just like pride is the ultimate evil, humility is the ultimate good.