Re: Are leagues "community business"?
I also must say that one part of the "spirit" of Teeworlds for me is it's open style (dunno how to call it), like invee01 already mentioned. I think it just is a fundamental part of Teeworlds that you can just download it, name yourself (or not) and join a server. So I would also advocate the optionality of the account system.
As I see in other games with accounts and stats, there's always a certain pressure connected to it. "Oh no, I've lost so many times in a row, and that with the grenade launcher! I have to do some kills now with that weapon to avoid ruining my stats..." You know, that kind of things.
Of course many people would like such stats nevertheless. More professional players might have a different attitude to this, and I see their points and respect that.
I also like the (pretty old) idea with the visible skill levels of the servers in the list, which could be made possible with the account system (although it doesn't necessarily require it).
So the account system has also many benefits and it could be wrong to just stay with the old and known things and don't try out something new. Stagnation might ruin a project.
I also thought about a seperation into the old "legacy" and an new account-based client, but that would be the wrong step to take, I think. Might as well put the optional account system in the client. Although it could make the whole account system more relevant, because it would not be optional in that seperated area. But it could split the community and would increase the amount of work, so no.
@the language support topic: Even if it was a lot of work, I can assure you that it wasn't useless and greatly enhanced the overall quality of the client for many players, imo.
Just my two cents.