Who laments over Mo'av?
Radak: The Navi speaks on behalf of the nation of Mo'av.
Malbim: Here it says that Hashem laments, for He enticed them not to flee 1 ; He caused their fall. In Yeshayah 16:7, it says that Mo'av will lament over itself.
Above (29), Malbim explained that they were told to flee, just they did not due to their pride! (PF)
What is "Kir Cheres"?
Rashi: It is a city in Eretz Mo'av. Radak - in Yeshayah 16:7 it is called "Kir Chareses." Malbim - that verse says "Tehgu Ach Necha'im." It was the 'hospital' to which they brought people wounded in war.
Radak citing Targum Yonasan: Their strong walled city.
What is the meaning of "Yehgeh"?
Rashi: Moaning like doves.
Radak: The mouth makes loud sounds and moans. The same applies to "Ehgeh ka'Yonah" (Yeshayah 38:14).
Radak citing Targum Yonasan: Mourns.
Malbim: Hashem will take all of Mo'av to Kir Cheres, for all of them will be ill or wounded.