This debate has been started on the German and Japanese Language & Usage sites, but I'm not sure it's been fully resolved. Should we tag each question (a mod would be the one to do the tagging; I'd be quite happy to if I were in the position) to indicate which language it was asked in? This would result in each question having a tag like
It is argued by some that these would be 'meta tags' and that they're bad because they don't mean anything unless combined with other tags, but I think they do mean something on their own: which language the question is in. Is this not useful information on its own which would allow francophones who wanted to filter out English questions to do so, and anglophones likewise?
(En bref) Faut-il indiquer par une étiquette la langue dans laquelle une question est rédigée ? Ce sont des méta-étiquettes, qui ne peuvent pas suffire à étiqueter une question, mais elles apportent quand même de l'information. Cette information n'est-elle pas utile, en particulier pour permettre aux francophones d'ignorer les questions en anglais et réciproquement ?