Vestigial features are a common plague in software. There’s a special type of this that often goes unnoticed. Vestigial features are usually usable features that simply aren’t used. But under the hood, every system has some code that isn’t even exposed. It doesn’t support a feature users can access. It’s often the result of experimentation, or perhaps a vestigial feature that wasn’t fully extricated. I like to refer to this as dead code.