How to understand "for all the notice anyone took" in this context?

Question

…Everyone wanted to know how he had done it, how he had tricked Dumbledore's Age Line and managed to get his name into the goblet.…

“I didn't,” he said, over and over again, “I don't know how it happened.”

But for all the notice anyone took, he might just as well not have answered at all.

“I'm tired!” he bellowed finally, after nearly half an hour.

I don't really get the phrase "for all the notice anyone took". What does "all the notice" refers to in this context?

Answer 1

First, compare it to a similar example:

https://www.macmillandictionary.com/us/dictionary/american/for-all-i-know "for all I know" - used for emphasizing that you do not know something. "He could be a murderer for all I know."

We might invent another phrase following the same pattern: "for all I noticed" - used for emphasizing that you did not notice something.

And then the original paragraph: "for all the notice anyone took". They did not notice, which is confirmed by the rest of the sentence - "he might just as well not have answered at all."

Answer 2

Sometimes for all refers to something which is quite substantial:

For all his strength, Samson could not budge the rock.

and has the meaning "despite {some substantial thing}".

And sometimes it is used ironically or sarcastically to refer to something very meager:

I could jump off a cliff, for all she cares.

It still means "despite", but the thing is, in the context of the sarcasm, actually not substantial at all, but meager. She cares very little.

Answer 3

The base idiom is: to take notice

You can often take any verb that collocates with a noun, and add "for all". But not always. This usage of for all usually involves perception, effort, abstraction of some kind or some other "force".

For example, here are some which come to mind: to take the trouble to do something, to put effort into something, to display courage, to counter arguments, to show weakness

All those kinds of expression can take for all.

• for all the courage he displayed
• for all the trouble you took
• for all the effort we made or put into x
• for all the weakness she showed
• for all the noise they made [noise=metaphor]

In the OP's example, for all the notice anyone took means, nobody took much notice of whatever it was. This "for all" can be used negatively or positively.

You should be rewarded for all the trouble you took. She should be reprimanded for all the weakness she showed.[police officer, for example]

It means: given the amount of x used, or given how much x.