The guidance from the OSM US Trail Access Project, as I understand it, is to tag operator= for paths which are “official”, because “official” basically means “there’s some entity responsible for it”. It allows for informal=no instead if the mapper knows that it’s a “formal” trail but doesn’t know which entity is the operator.
I feel like explicitly tagging informal=no is better than having no informal or operator at all, so I think there’s value to it existing. But it’d be better to just map the operator (and operator:wikidata) if possible. (And then I’d agree that a path with an operator on it no longer needs an informal=no tag.)
I’m not sure if this theory is specific to the US (or at least what OSM US is trying to standardize), and maybe other countries think of mapping their trails differently?
