When did he stand in front of the gate?
Rashi: It was every morning.
What is "Al Yad Derech ha'Sha'ar"?
Radak: A place on the path to the gate. Malbim - the gate was special for judgment.
Why did Avshalom sit to greet people coming for judgment?
Malbim: He showed his humility, his love of righteous judgment 1 , and his love of the nation.
Surely he did not rule in practice. That would require both litigants to be there, and then he could not tell each "your words are good and proper"! Rather, it was to show how much he loved judgment, and wanted to become king in order to be able to judge everyone. (PF)
Why did he ask which Shevet he is from?
Malbim: He showed [feigned] love for the person. (Also refer to 15:2:5:1.)
Did the person say "me'Echad Shivtei Yisrael"?
Rashi: No, he named the Shevet he was from.
Malbim: If he said that he was from a Shevet other than Yehudah, Avshalom would say that therefore, the king will not hear his case.