A basic comparison with parallelism question:

Consider the two sentences:

1. Covering the floors with tiles costs twice as much as covering them with linoleum.

2. Julia was able to climb the tree as fast as her brothers did.

Both the aforementioned sentences are deemed correct but, ofcourse they are different. sentence 1 does not ends with a verb "does". If 2 is correct, 1 should also be re-written as

Covering the floors with tiles costs twice as much as covering them with linoleum does.

Now, am i missing something here?

No response? This is either a too dumb question or a too difficult. I doubt the latter is the case here ;)

yep, you're missing this: you only need the extra helping verbs to resolve an ambiguity.

in sentence (2), there's technically an ambiguity if you DON'T write 'did':
julia was able to climb the tree as fast as her brothers
the sentence could mean what it's obviously supposed to mean (i.e., julia could climb the tree at the same speed as could her brothers), but it could also, grammatically, mean that she could climb the tree as fast as she could climb her brothers. (that must be a really short tree.)
i say 'technically' because you have to be EXTREMELY LITERAL in your interpretation of these sentences. even if one meaning is obviously preferred to the other by way of 'common sense', that's not good enough; you have to have a sentence that is grammatically and semantically unambiguous.

analogy:
i know more about shakespeare than my brother --> problematic, because this could mean i have more shakespeare knowledge than my brother does, or it could mean that i know more about shakespeare than i know about my own brother.
fixes:
i know more about shakespeare than does my brother (if you mean the former)
i know more about shakespeare than about my brother (if you mean the latter)

--

in sentence (1), there is no ambiguity (try to conjure an alternate interpretation; you won't be able to), so you don't need the auxiliary verb.

[quote="RPurewal"]

Dear Ron,

Is the sentence "I know more about shakespeare than does my brother"correct? Because it seems to me that the sentence isn't parallel. "I" matches with "my brother" and "know" matches with "does". Therefore, in my opinion the sentence strictly should be "I know more about shakespeare than my brother does." Is there anything that I am missing, maybe sth. about the comparison. Or do you have any conflicting example that you saw in OG.

Thank you very much..

in formal written language, these sorts of helping verbs are placed before the noun, so "...than does my brother" is indeed the preferred version.
this will of course SOUND wrong, because that isn't the way we speak. but, after all, spoken english and written english are effectively 2 different languages, so it shouldn't come as a surprise that there are differences (many of which are much more pronounced than this one).

in case you care about why, here's why:
if you place a long enough modifier after the noun, then the helping verb gets "orphaned" if it's placed afterward (as in the spoken convention):
i know more about shakespeare than my brother, who has never studied literature in school, does --> ugly and hard to read (it's difficult to tell the subject of the word "does")
i know more about shakespeare than does my brother, who has never studied literature in school --> still easy to read and process
this issue is nonexistent in spoken language, because we don't speak with these sorts of long modifiers. if we were going to speak this sort of sentence out loud, we'd most likely express the idea of the modifier in an entirely separate sentence.

hth.