I never understand examples like that. The point of hanging routine punctuation (or letters and numbers, for that matter) is to give the margins a nice, even lo

I never understand examples like that. The point of hanging routine punctuation (or letters and numbers, for that matter) is to give the margins a nice, even look to the human eye. The adjustment is too subtle to notice when reading, but tidies up the overall design of the page. However, arbitrarily shoving an entire symbol outside the text body doesn’t achieve that. If anything, it is often worse than just mechanically aligning everything: instead of slight indentations, which the reader’s brain will “fill in” up to a point, you’ve now got glaring protrusions, which break the pattern in a way we don’t gloss over so easily. I think the article you cited gets it right when talking about hyphens: they can usefully move out a little, to even up the “indent” effect, but in most fonts they shouldn’t move over the whole way. However, the same advice holds just as much for any other symbol.