Now I have an explanation for my mental model gap.
As you can see, you don't need to use any special type of characters to mark a URL as such. The tricky part comes when somebody wants to insert a URL with a description text.
I view this as broken. I'm not inserting a URL with description text. I'm inserting text that happens to also point to something else.
Text-followed-by the URL, consistent with text-followed-by a footnote indicator.
As you can see, you don't need to use any special type of characters to mark a URL as such. The tricky part comes when somebody wants to insert a URL with a description text.
I view this as broken. I'm not inserting a URL with description text. I'm inserting text that happens to also point to something else.
Text-followed-by the URL, consistent with text-followed-by a footnote indicator.