help with a phrase from 21.3

This phrase appears in 21.3

As far as I know there are two possible situations where die replaces Sie. One (according to Michael Thomas anyway) is in conversation where it is not clear that a spoken Sie refers to they rather than you (it would be obvious when written because with the full verb ending Sie is capitalised for both you polite singular and plural but not for they).

Die is also used where there is a negative aspect or implied criticism in the statement. This is referred to as the 'finger pointing' use.

 

Thank you Fred-C14, I didn't realise that replacing personal pronouns with der/die/das was a "thing".
You have given me a good pointer to a little research. :-)

I am guessing this is a colloquial use of the demonstrative pronoun. I don't think using sie would be ambiguous from the context.

I didn't see it as particularly ambiguous either so you are probably right about it being colloquial. Germany is a big place and there are all sorts off odd little language quirks, a bit like Britain in that respect. 

There is another issue with the phrase, ob is a subordinating conjunction. 
I put the two versions of the phrase (die/sie) into Duden's grammar checker and it accepted both versions but recommended that there should be a comma  after nicht. 

The thing that threw me was that "they" referred to something nebulous rather than something directly referred to previously.

I certainly agree that there should be a comma after nicht. Obviously this wouldn't be apparent in spoken conversation but it should really appear in a written answer.

 

Hallo sfpugh and Fred, 

you are right - there is supposed to be a comma after "nicht". 
I'll add that in right now. 

Thank you for letting us know. 
Leah von Rocket Languages