Another piece of evidence in favor of "the debate rages" (though IMO more in favor of double-spacing): if typographers were even slightly unified in this, you'd

Another piece of evidence in favor of "the debate rages" (though IMO more in favor of double-spacing): if typographers were even slightly unified in this, you'd see period-double-space ligatures that render as period-single-space. Instead, I'm not aware of any common fonts that do this.