Question: why klingons look that way in the 23rd century?
Answer: Basically, Augments were the genetically engineered humans from 20th Century Earth. ... That's right: Khan's super-human DNA getting mixed with Klingon DNA is what caused a bunch of Klingons to look more human in the 23rd century. Presumably, Klingons like Kor got their ridges back at some point as they got older.