Learn English – Why is ‘So’ being used to begin an anwer to a question grammatically incorrect

The Oxford Learners Dictionaries defines worse as, among other things, less good. So I suppose if OLD can use less good, so can we. Still, when comparing two good things I would say:

A 90% score is good, but not as good as 100%.

My admittedly foreign ears don't like the sound of less good than. Google search concurs: not as good as beats less good than 6,000 to 1. This English Grammar advises against less good than on the grounds that "[w]hen making negative comparisons less tends to be used only with multi-syllable adjectives."

Five months later I’m tremendously upset that fickle Google search has not as good as beating less good than 470 to 1 only. I swear it was 6000 to 1 when I first looked into it. Oops, it’s only 17 to 1 in the Ngram. But I include it below hoping it proves more constant. The first few pages of Google books search for less good than return almost only religion and philosophy books. They have more good too (my emphasis):

A degreed property is a property that can be had in different degrees. Goodness is an obvious example of a degreed property. Something can be more good or less good than something else. (David E. Alexander, Goodness, God, and Evil, Continuum, 2012, p. 115.)

It is grammatically correct in this sentence, but there are conditions where it would be grammatically incorrect. The "more" in your example is modifying the verb "cover," whereas I believe you're reading it as modifying the adverb "later." "More" is clarifying the comparative degree of the verb (we will cover it in more detail than we just covered it now), while "later" is indicating when the action of covering the topic more will occur.

However, if the speaker meant to use "more" to modify "later," such a sentence would be gramatically incorrect.

Example: "It's much more later than my bedtime right now."

As you can see, this would be grammatically redundant, as the word "later" already means "more late." So, to modify it with the word "more" is unnecessary.