Make it consistent with itself

This project was built across many separate conversations and the
style has drifted: <paste several files>

Find the inconsistencies:
- Naming — camelCase here, snake_case there, different words for the
  same concept.
- Error handling done three different ways.
- Async handled with promises in one place and callbacks in another.
- Different patterns for the same kind of operation.

For each: pick one convention, say why, and list every place that
needs changing. Don't change anything yet — I want the list first.