From what I've seen, some members of this forum do not have the most fluent grasp of the English language, which serves as this site's main mode of communication. Should we permit questions in other major languages, namely French, Spanish, and/or Yiddish and German? (The language of Hebrew is excluded from this proposal as it may warrant a different discussion.)
No; we should not. We have built a community of experts who are fluent in English, who are capable of answering, evaluating, voting on, improving, maintaining, categorizing, moderating behavior around, etc. content in English. We have not built a community that assumes fluency in any other language of discourse. To build such a community effectively would required a significant bootstrapping effort - much more than simply beginning to allow content in other languages. Such efforts are what the Stack Exchange new site staging process is for. Allowing content in non-English languages without first doing the requisite community-building would result in portions of our content repository being systematically under-maintained and therefore of significantly lower quality.