Can I suggest something? Because, well, this could be too much restrictive in my opinion. AND, you can't make comparison between voice and text chat, really... Text chat is completely less problematic than voice one.
If you really want, you can allow not only English in text chat, but only ALL Romance Languages + English.
You know, guys, most of us are European. And, more or less, Romance Languages can be understood. Reading them in text chat is different than reading a (for example) Russian sentence, you know. (nothing against Russians, for example, but it's fact of understanding at least some what people write in text chat).
Romance Languages (French, Italian, Spanish, Portuguese...+ English) could be the only allowed in text chat.
The fact of German language? Well, if you want add also this one.
It's not racism/ discrimination/ whatever you want to call him, but it's realism: our community is of European mould. I'm ag
against this limit.
Anyway, if I can say this, the problem is not really text chat, Inu: there are many and many other problems to think about. Making limits to text chat is very bad. The problem is SPAM itself, not using "strange" languages.
Discussing about languages is quite silly, really... The only problem is the Spam, as I said (which can be in all the languages you want, also English... MAINLY English).
And, at least in the whole experience I have of being Admin, NOBODY has cared of languages in text chat (maybe just 1/100 people complained about Russian/Arabic characters, but 100% sure about European languages, that nobody cared of them so much).