You are a developer and you want to keep your project moving forward. You set up various communication channels and organize an open community around. Your vivid project starts to attract new people, amongst them are people who intend to contribute code to the project. Great, because that’s what you were waiting for when you started building your FLOSS community.
Naturally, you do not allow anyone on the net to directly contribute code without any, more or less formal, review process. That’s good, since you care about happy community of contributing members, but you also want quality that you can be proud of.
And then there’s the world of community localization. You are most likely not a polyglot, and you can hardly do a review process with tons of languages from around the world, apart from making sure that the localization work you’ve been provided is not missing some obvious bits of technicalities. So you simply open the submit process for l10n to anyone, or reach to some nice outsourcing tool, hoping that translators will eventually cope with it and the project’s l10n will be worthy, as is the code. But really?
But Really, It’s For Your Own Good
That is, not to stick to the openness at any cost. The fact is that, quite similarly to the code contribution, the quality work in l10n will not miraculously show up. It needs reviews, proper management, suitable workflow. It needs community.
One of the first things you need to do if you want to facilitate building a real l10n community is to set up, more or less formal, rules. So you turn the translation teams option on. You encourage work in translation teams & projects, so your translators can interact with each other and share knowledge. You keep an eye on l10n. You are responsive to the needs of your translation team members. Then you are a great developer with FLOSS project that deserves quality & efficiency in l10n very much comparable to that of the professional (as in commercial) translators with plenty of ISO & DIN certificates. And your project has it. For free. (Almost.)
Lets also not forget that broken translations can crash your application (I’m myself guilty of doing this countless times, one learns the hard way), so the quality is l10n is not some luxury thing.