Neither...nor

These are right:

She didn't return that night or the night after.
She returned neither that night nor the night/one after.
I can't eat or sleep.
I can neither eat nor sleep.
I can't confirm or deny.
I can neither confirm nor deny.

I thought I could use nor after a negative statement when adding another negative statement. As in:

She didn't return that night, nor the night after. - Why do you prefer 'or' in such cases? Here's what I've read about 'nor':

It's a British thing?

Oops. Epic fail.

Are the following sentences correct?

Neither his son nor his daughter nor his mother were at the funeral.
I can't eat or sleep or walk.

You know I died, right? And Boonie used magic to bring me back to life. Ever since I came back I've been seeing things I shouldn't be seeing.

Would the last sentence make sense if I omitted the 'shouldn't be seeing' and added 'shouldn't see'? And what's the difference between them in this case?

Yes, somewhere I read that more than two like that are in (accepted) use.

I can't eat or sleep or walk. - Does this sentence sound natural? It does, to my ear.

I can neither eat nor sleep.
I can't eat or sleep.

The meaning is the same. But, is the first one more formal? What's the difference?

Neither...nor is the more formal correlative conjunction in my book.

Will you tell me what the difference is between I have just and I just? As in: I've just eaten. and I just ate.
I've noticed that my friends that are from the UK use present perfect much more than people from the USA. I tend to use I just + past simple. Is the first one more formal? :?

The difference is the same as for almost any simple past vs present perfect use. See CJ's comments here:

AnonymousI've noticed that my friends that are from the UK use present perfect much more than people from the USA. I tend to use I just + past simple. Is the first one more formal?

You have no