Pressing ⌘I (or using the UI equivalent) should act like the italics version of caps-lock.
A sentence with italics or any other emphasis should read exactly the same without that emphasis. Where the same isn't true of capitalisation.
But it doesn't, that's the thing! The word you italicize can alter the meaning of a sentence. For instance:
> I didn't steal Sally's necklace!
> I didn't steal Sally's necklace!
> I didn't steal Sally's necklace!
I didn’t say I took the money.
I didn’t say I took the money.
I didn’t say I took the money.
I didn’t say I took the money.
I didn’t say I took the money.
I didn’t say I took the money.
I liked ChatGPT's example, but I thought it was a bit too subtle, so I changed it to the sentence I used in the GP. I didn't realize ChatGPT's example was plagiarized.
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1: ChatGPT wrote "I didn't say I took her money."
• The first version implies that I acquired Sally's necklace via other means.
• The second version implies that I stole someone else's necklace.
• The last version implies that I stole something else from Sally.
Not true. In conventional English, it is typical (if not expected) to add verbal emphasis to italicized words while reading aloud.
In Chrome, if you copy CSS-all-caps text to the clipboard, it is copied as uppercase.
Intriguingly, in Firefox, it is copied as the original (mixed case) source HTML text.
I do like the idea treating all-caps as a style, just like small caps. The problem, of course, is that it makes it kind of impossible to type within it, since there's no feedback as to when you're typing capital letters at the starts of sentences or not.