New players

So you've got a group and you've played to about... oh, let's say level three. And then somepony else wants to joing. What do?

I'd say add em at level three, and stop handing out harmony points until your group works well together, or accomplishes something big together. Really I think it depends on how well the new character is integrated into the story itself. Is this character a complete stranger or a longtime friend of the group, or just some minor acquaintance. Of course I'd also ask my players what they would prefer.

Personally I enjoy having them join at level on and then level them up quickly after the session... That was how it happened in Pony Team Bravo and that was quite fun. :3

But for a Play by Post game, I'm not sure how you'd make that work...

As I believe I've said elsewhere, in my experience there is no benefit to having any member of the party ever not be of the same level as the rest. It would really be better for GMs if they thought of level as a thing that was a quality of the entire party and not individual members.