How important is a plastic-free interior?

This is a recurring concern in tea and plastic-free-living community threads. Many budget kettles use a plastic gauge window, lid, or filter that contacts hot water. If you're sensitive to plastic taste or want to minimize contact, look for kettles that explicitly advertise stainless-steel-only or glass-only interiors — and check that the lid and spout filter are also metal, since that's where manufacturers commonly cut costs.