Which "wider audience" are you talking about? My target audience is the data consumers, and the language to tell them is the OSM tags. My target audience is *not* Nehegreb or Kevin Kofler, and they don't even want to know. Otherwise they would have asked me. They never did!

There's no "correct" way of mapping sewers, as they are rarely mapped. As far as I know, I'm the only one who has ever mapped a sewer in Austria. I wasn't even sure which waterway=* tag to choose, because there's zilch documentation on sewer tagging. Where no tagging scheme exists, mappers can make up their own ("use any tag you like"). But either way, it should be up to the mappers and experts to work out tagging schemes. You can't dictate pilots how to tag airports when you have never even seen one.