Demo and kedo used in the same sentence?

Question

My penpal wrote this (he was correcting my grammar):

でも、ほぼ大丈夫だけど、”改めてもらってもいいですか。”の方がもっと

良いですよ。

Why is kedo used as well?

Answer 1

Usually demo is used to start a sentence and kedo is used in the middle of the sentence, like you can see in the sentence your penpal wrote. And as far as I know, demo is more polite than kedo.