If they wanted people to use a different tag for such text, they should have created an idiomatic tag instead of attempting to repurpose existing ones. Adding alternative elements is usually the better solution.
If you read the spec, it mentions several different uses for <i>, depending on the context. Otherwise, we’d need a different element for each context, bloating the spec by having special purpose elements instead of general ones.
For example, <i> is used for ship names:
<p>They came over on the <i>Mayflower</i>.</p>
Turns out, if you look at the Wikipedia article about the Mayflower, the name is marked-up with the <i> element [1].
In general I think many UXs are too shy about using italics.
“Are you sure you want to delete the user you piece of shit?”
Options:
> Yes, you worthless dildosaurus
> No! Stop! I hate you!