Like many languages (but unlike Greek or Hebrew or English), Tuvan uses a formal vs. informal 2nd person pronoun (a familiar vs. a respectful “you”). Unlike other languages that have this feature, however, the translators of the Tuvan Bible have attempted to be very consistent in using the different forms of address in every case a 2nd person pronoun has to be used in the translation of the biblical text.
As Voinov shows in Pronominal Theology in Translating the Gospels (in: The Bible Translator 2002, p. 210ff.), the choice to use either of the pronouns many times involved theological judgment. While the formal pronoun can signal personal distance or a social/power distance between the speaker and addressee, the informal pronoun can indicate familiarity or social/power equality between speaker and addressee.
In these verses, Ziba uses the respectful pronoun as he addresses David (1 Sam 16:4) in the Tuvan translation, whereas Shimei uses the informal pronoun, compounding the insult given by his words (1 Sam 16:7-8).