People can and do have "private" discussions about articles via email. Is
there any rule prohibiting this?
Is there rule against discussing articles on this mailing list (knowing full
well that not all Wikipedians subscribe to this list?)
Is there any rule that forbids any discussion of an article anywhere except
on that article's Talk page?
If the answer to the above is "no," then what possible objection can there be
to non-English discussions on a talk page? These discussions are _more_
public and accessible than _any_ of the above.