In the examples with the em-dash, yes, you could replace both with a colon or a comma or something. But there's an aesthetic difference. There's something almost ironic to the last sentence with the em-dash, but it would become a banal statement with a comma.

Okay, em-dash rant over. Promise.

And yes, proper usage of em-dashes can be confusing. My rule of thumb is:

1. Colons indicate a linear relationship. (e.g. The rat: a tiny rodent.)

2. Em-dashes can indiace a linear or a contrastive relationship. (e.g. Lions—the kings of the jungle.
OR
Lions are the kings of the jungle—or the zoo)

P.S. Thanks to @saken.me for convincing me to serialize my yapping and turn it into something interesting and potentially educational (one day!)

I think you will be seeing more posts like this in future :^)

I think this system makes for a pretty fun way to distinguish between all the different stuff I get up to in my life.

And if you want to see even more weird, cool things from this book (that's more like lit crit than this grammatical analysis) take a look at the article I wrote about it last year:

These ₁ and ₂ distinctions are differentiated in some way that's never revealed to us in the original language (maybe it's a specific sound or syllable). They're separate from the base word, but change its meaning, making them more like some kind of universal work-based suffix

The sociopolitical implications of this aside (though they're interesting for sure), I want to discuss this from the PoV of grammar. This isn't just using numbers to distinguish between two untranslatable words of a future language. You can talk about colleagues₁ and an office₂ and being busy₁ and ₂

The story is set millenia in the future, on a socialist planet part of a galaxy-spanning civilization. The planet distinguishes between "jobs₁" which you work at for yourself, and "jobs₂", which you work at for your society. For example, the protagonist works as a diplomat₁ and a waste collector₂

It's ironic because the sensor-activated blow-dryer they had is worse for germs than getting your hands dirty and cleaned with regular towels.

Some Goodreads reviwers will literally sit there yapping on about how Mark Earlington was tracking down the Mysterious Lady for 3 paragraphs and make ME sift through their tepid water writing to find any crumb of their opinion on what they actually read!!!!