As far as I can find, the New King James Version may be the only translation that puts a proper name in Psalm 99:8, which makes it very intriguing. Psalm 99 describes the holiness of the Lord and the awe, exaltation and praise that is due unto Him. The Psalmist mentions Moses, Aaron and Samuel specifically, who all “called upon the Lord and…kept His testimonies and the ordinance He gave them” (99:6-7). Then, the Psalmist addresses God directly and says, “You answered them, O Lord our God; You were to them God-Who-Forgives…”
Moses indeed had seen the forgiveness of God frequently in his dealings with an ungrateful Israel. Aaron had seen the forgiveness of God after making the golden calf. Samuel had seen the forgiveness of God in his dealings with a self-willed nation and king. They could easily and appropriately address the Lord as and even begin prayers with “Dear God-Who-Forgives…”
What do you call God? Lord? Jehovah? Loving Father? How about God-Who-Forgives?