id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
9182	checks for layer=-1 on waterways	RicoZ	team	"I have seen some users tagging whole rivers, canals, and riverbanks with layer=-1 with no valid reason - sometimes for a whole country or region. It would be great if the validator could issue warnings in such cases.

As far as I can see there is a quick and easy check: a waterway that is not a tunnel should never ever have layer=-1. Only when two waterway tunnels are crossing an extra layer tag may be required. This would catch over 99% of cases with minimal effort.
"	enhancement	closed	normal	16.06	Core validator		fixed		RicoZ