A does the same B as does C

Solution 1:

While subject-verb is the more natural order for English, the inversion to verb-subject can be used in certain situations. To better understand this, consider these sentences, all of which could be considered valid (some more acceptable than others):

• S1: John jumps as high as Jim jumps high. (This is technically valid grammar but not acceptable style. Compare with the more valid style of "John jumps as high vertically as Jim jumps horizontally".)
• S2: John jumps as high as Jim jumps.
• S3: John jumps as high as Jim does.
• S4: John jumps as high as does Jim.
• S5: John jumps as high as Jim.

These are ordered from S1 to S5 with increasing focus on "Jim". Note the first three are parallel constructions Noun-Verb Noun-Verb as follows:

Noun1-VerbPhrase1 as Noun2-Verb2.
Part1 as Part2.

Even within a parallel construction, S3 is better than S2 which is better than S1 because each is better at helping the reader to focus on the only important information in Part2 which is Noun2 (Noun2=Jim). Since it's a parallel construction, the only difference is Noun2, and anything that distracts from that would make reading the sentence more difficult.

In contrast, S4 distracts the reader because "does Jim" is grammatically more awkward (in English) than "Jim does".

S5 ("Noun1-VerbPhrase1 as Noun2") could be ambiguous: can John jump Jim's height? But S5 could be the most succinct given the proper context. Suppose a high-school student, John, completes a high-jump of 8 feet. A talent scount might exclaim, "Wow! John jumps as high as Javier Sotomayor!" (Sotomayor is the men's high-jump record holder of about 8 feet in 1993.)

Now consider the following sentences, all of which could be considered valid (some more acceptable than others):

• S1': Objective-C supports the same conventions for specifying strings as C supports conventions for specifying strings. (Only technically valid grammar.)
• S2': Objective-C supports the same conventions for specifying strings as C supports.
• S3': Objective-C supports the same conventions for specifying strings as C does.
• S4': Objective-C supports the same conventions for specifying strings as does C.

Here, S1' demonstrates the problem with redundancy. S2' is obviously better than S1'. S3' abstracts "supports" into "does". But S4' is the best at helping the reader to focus on the only important information in Part2 which is the word "C".

The form one uses for Part2 depends the length and complexity of Part1. Very simple sentences can be formed with the parallel noun-verb noun-verb while more complex sentences may be more readable with the inversion noun-verb does-noun.

Solution 2:

Inversion is not at all unusual, though not mandatory, with the similar-looking

I often take the train to work on Saturday – as does John.

I often take the train to work on Saturday – as John does.

This may well be influencing your questionable sentence.

I often take the same train to work as John does.

(I'd prefer 'that' here, but Swan licenses 'as' also) uses the normal word order. The 'does' is often dropped.

I often take the same train to work as does John.

(This sounds unnatural; I wouldn't say it's ungrammatical, and the weightier DO 'the same conventions for specifying strings' makes 'as does C' sound less unnatural.)

Solution 3:

There are a lot of different types of subject-verb inversion and subject-auxiliary inversion in English.

I mention "subject-verb" and "subject-auxiliary" inversion separately, because inversion is much more common with auxiliaries than with other verbs.

They also differ in how acceptable different people would find them, but this is an example of subject-auxiliary version that is clearly correct.

This particular case is with anaphora where we can only understand the meaning of the auxiliary in the context of the preceding clause or sentence ("as does C" or "as C does" would each be meaningless on their own).

This can be used for comparison here, and also for adding information:

Alice sleeps, as does Bob.

We add the information that Bob sleeps based on what has been said about Alice. In this case, the inversion is clearer than the non-inverted form:

?Alice sleeps, as Bob does.

This is unclear as to whether it's adding the information that Bob also sleeps, or saying that the way Alice sleeps is in some way similar to the way Bob sleeps (without the comma it would more strongly suggest mean the latter).

In the case of the question, the lack of comma means that there is clearly a comparison being made.

Here, either "as does C" or "as C does" would be definitely acceptable.

There's little to choose between the two. But note:

*Objective-C supports the same conventions for specifying strings as supports C.

Objective-C supports the same conventions for specifying strings as C supports.

When we use this form with a verb other than an auxiliary, we're on much shakier grounds. While there are other cases where subject-verb inversion happens with English, the first of these last two examples would be unusual at best.

Solution 4:

First, subject and verb were "transposed", not "replaced". As the answers to your other post mention, this transposition tends to de-emphasize the verb and emphasize the subject. One place were we always do it is "So do I." "So I do" means something different:

I have vanilla ice cream on my shirt.
So do I.

Here I am saying that I also have vanilla ice cream on my shirt.

You have vanilla ice cream on your shirt.  
So I do.  

Here, I am simply saying that I agree with the person making the statement.