Active editors has historically been defined as the number of users who make 5 or more content edits in a month, since this number is so widely used in the movement, we don't want to redefine it without a consultation process.

On the other hand, new editor retention was separately defined by @Halfak who (understandably) didn't attempt to harmonize it with our active editors definition. He used all edits, because he sees talk and project namespace edits as also representing important wikiwork, and so far, I've mostly stuck to his definition.

We should resolve this inconsistency eventually, and my inclination is that we should focus primarily on all edits rather than limiting it to content editors. However, since these are movement-level metrics, this will require some amount of consultation (for example on wikimedia-l 😯). It may also make sense to tackle this as part of a larger revision of contributor metrics.