I don't like him as much as you.
Dear Mirium, here is my analysis.
1-a. She doesn't sing as well as me.
1-b. She doesn't sing as well as I do.
In 1-a, an object pronoun is used after 'as', according to Michael Swan, this is an informal style, whereas in 1-b, subject+verb is used after 'as', it is more formal.
As you can see, in your example #2
#2. I don't like him as much as you.
2-a. I don't like him as much as you do. ( 'you' is a subject)
2-b. I don't like him as much as you. ('you' is an object pronoun)
2-a and 2-b are possible variants of #2. Have you noticed that we have a subject 'you' and an object 'you'?
In 2-a, both of us like him, but I like him less and you like him more. Ambuguity is cleared out in 2-a because 'you' is a subject.
What are the two equal things you compare now?
1. I don't like him. (subject)
2. You don't like him. (subject)
You are comparing who likes him more, You or I ?
In 2-b, I don't think it's usual to regard 'you' as a subject. For example, He doesn't like her as much as we. (Sounds weird to my ears). You either say 'He doesn't like her as much as we do or he doesn't like her as much us. So I don't think 2-b is that ambiguous. (It could be.) So 2-b means I don't like him as much as I don't like you.
What are the two equal things you compare now?
1. I don't like him. (object)
2. I don't like you, either. (object)
It's the object of the main verb that is compared. In other words, I dislike him more, and I dislike you less.
TransformationStep 1I don't like him as much as you don't like him.
> I think this sentence is gramatically strange. 'As + Adj/Adv + as' is used to compare two equal things. Here in the sentence, you compare the feeling of 'dislike him'.
Step 2
I don't [like him as much as you like him.]
>'don't' negates the idea in my brackets. Is the negation scope here?
Step 3Then, I'd apply 'pro-verb' substitution to the latter 'like him', and then it generates a new variants,
I don't [like him as much as you do.]
So the latter 'like him' is within negation scope.
What do you think, Mirium?