Kettle Etiquette (Ketiquette?)
1. If there are others in the room, or possibly expected shortly, don’t just boil enough for your own cuppa.
2. Don’t go off at a forward planner guest/visitor for “putting too much water in”.
(Further additions welcome.) 
I swear, there are some people for whom no matter what size the kettle, they cannot abide by filling it up a decent amount. May their lives be blighted by failed elements and cold drinks on a winter’s day.
