I see, this is even documented somewhere (although you did not provide a link).

I think this is generally a lost cause. Whatever tools interpret the changelog should be taught about common indent characters, and make use of the whitespace as a hint.

There is the changelog generator service which meticulously follows the recommendation but can be used only in very specific cases. In any other case you basically get free text typed by a human, not following any specific formatting to the letter (intentionally or not).