Since you posit that there is a risk, it's up to you to say what you think the risk is. Do the benefits of allowing users to post images outweigh the risks involved? Do the benefits of allowing claims that Java is a real programming language outweigh the risks involved? Do the benefits of allowing teen moderators outweigh the benefits involved? Do the benefits of allowing users whose name begins with Z to ask questions outweigh the risks involved?
it risks fragmenting our knowledgebase over multiple languages and segregating our users.
In your whole question, this is the one line that explains your position. That's not much to go on.
Why do you think that having SO-like sites in other languages would fragments the knowledge base of SO? Roughly speaking, there are three kinds of programmers in the world¹:
- Those who are comfortable participating on a site in English. They won't be affected by the existence of SO in other languages.
- Those who can read English but not express themselves. They can benefit from SO, but they can't contribute.
- Those who can't speak English at all. They can't even benefit from SO.
Creating SO sites in other languages will drive programmers of type 2 away from SO. But they weren't contributing to SO in the first place, so SO isn't losing anything by it.
A slew of unwarranted assumptions
A lot of the claims in your question are plain wrong.
English is, essentially, the world's lingua franca
That is true (for programmers — programmers tend to be better at English than the average profession), but only to some extent. There are many type 3 programmers, and even more type 2 programmers. Of course, you don't tend to meet them on SO or other English language venues: the language excludes them.
If you search the web a little, you will find forums about programming in Chinese and French and Russian and Portuguese and other languages. There are clearly people who do want to converse about programming in languages other than English.
Why are we suddenly forgoing Stack Exchange's Non-English Policy in favor of fracturing our userbase?
Stack Exchange has never had a non-English policy. It is rather bizarre that you should make this claim, considering that you cited an official post by Stack Exchange founder Joel Spolsky stating that there is no such policy:
it is OK to propose new sites in other languages. (…) For example: (…)
The non-English question policy is for the existing sites. Stack Overflow is English-only. As Stack Overflow founder Jeff Atwood put it:
It is not, nor has it ever been, our goal to be the one place in the world for all programming information in every possible human language.
All of this applies to Stack Overflow and the other sites of the original trilogy. SO was and is about programming, in English. Stack Exchange is a different thing altogether: SE sites can be about any subject, in any language.
We need to see charts of activity by country to gauge how many people this would bleed away from the main site. My guess is, it's a lot more than you'd expect.
I have no idea how many people Emrakul expects to find, but that number is irrelevant anyway. How would charts of activity by country tell you anything? The people who are participating on SO now aren't going to stop if there are sites in other languages. The ones who are on SO now are the ones who are comfortable enough with participating in English. Most of them are going to stay. SO in other languages is largely intended for the people who are not participating on SO now, because they can't.
Your follow-up questions
Why should language variants be allowed?
Why not? You've yet to explain why they shouldn't be. And as you acknowledge, there's an official policy that they are allowed.
Does the reward really outweigh the risk of dividing our user and knowledge bases?
Seeing that you don't seem to be able to articulate why there would be a risk, that doesn't put much of a burden on the reward. For the current participants in Stack Overflow, there are several rewards that may be small but still nice to have. There will fewer incomprehensible posts by people who just can't make themselves understood in English but currently have nowhere else to go. There will be a place where answers from non-English-speaking programmers can be found, when such answers are currently buried in the webforums that SO sought to replace if they exist at all on the web. For the people who cannot participate in Stack Overflow due to the language barrier, the reward is considerable: they will gain access to a questions and answers site about programming.
A glaring omission
Nowhere in your
rant question do you consider the benefits for the programmers who don't speak English enough to participate on SO. They would gain the same benefits that you and I gain from SO. That is a considerable gain that would outweigh a significant cost to SO — and that cost has yet to be demonstrated.
If you can have nice things, why not let others have them too?
¹ Plus those who don't understand that you can count to 3 even in binary.