As a designer who also loves typography, I should apply all these rules in any situation, right?

I don‘t. Because:

1️⃣ Nobody, except a few typography nerds, gives a damn.

2️⃣ If you‘re concerned about the language dying, because of how people (don‘t) use emdash, go read and write poetry, focus on the message and storytelling.

If you‘re deep into it enough, the correct form will remind itself.

3️⃣ All that said, I‘m always doing my best when designing a classic physical book, for that is a medium that still deserves respect...

4️⃣ …but I also like to bend or break rules. But it must be done consciously and in sync with the topic/style of writing/…

According to see emdash and assuming it‘s AI generated, I used to think like that, but I don‘t anymore.

I‘m using AI to consult some of my texts with, and sometimes it‘s that I just copy paste few words or a sentence into my own text, and if I forget about the emdash there… sue me.

My conclusion: Know the rules, but better think about the message.