No, it has been implemented everywhere but on the “add sentence” and “add translation” forms.

> I personally don't think the problem is due to the restriction of the list but due to the fact that the rules and the form are not very clear for new users.

I think it’s both. If you look cindycute’s profile, there is only English while he or she’s a native Chinese. When people are learning a language, and they are asked to add languages they are interested in into their profile, it’s normal they don’t add their native language. Who would know? Even when you’re adding a new language into your profile because the “add sentence” or “add translation” form told you to do so, it’s not clear that we mean your native language rather than the language you want to add sentences in or translate into.

We could solve this problem by having the following process:
• Bring back the full list of languages, with autodetection selected by default.
• Autodetect the language *before* submitting the sentence, so that the user is aware of what language he or she’s about to submit.
• If the selected language isn’t in the user’s profile, display an error message “Sounds like you’re trying to add a sentence in X, but you didn’t add this language to your profile.” And if X was autodetected: “If the sentence was mistakenly detected as X, please select the correct language.”