Here’s the original sentence:
The days were too short, and, strangely, tomorrow, with its news reports, new bits of information, new insights, tomorrow seemed unreachable until all at once it had been there and was yesterday.
Here is Rachel’s corrected version:
The days were too short. Tomorrow, with its news reports–new bits of information, new insights–tomorrow seemed unreachable until all at once it had been there and was yesterday.
This is a good use of dashes. Notice, too, that Rachel made the original sentence even more manageable by breaking it into two; she also deleted two words: and and strangely.
The only thing that I would debate is the location of the dashes. In the original, news reports, new bits of information, new insights, have equal weight and are independent of each other. Rachel’s placement of dashes assumes that new insights and new bits of information flow only from news reports.
Since humans also gain insights and bits of information through reflection, conversation, direct experience, and in other ways, I’d preserve the original independence by placing the dashes in a different location. Also, because removing and and strangely changes the meaning, I’d leave them in. But I would delete the second occurrence of tomorrow:
The days were too short, and strangely, tomorrow–with its news reports, new bits of information, new insights–seemed unreachable, until all at once it had been there, and was yesterday.
Note that I also added two commas, to slow the pace of the sentence.