In my opinion, I think WSDC participants can be allowed to speak their mother tongue.

I'll be sorry to you. If I can predict this debate progress this interesting way, I must have set 5 round on this debate. But anyway, this is my last turn, so I start my final reply in this debate. Your examples are attached too much importance to English Speaking World and European countries. I'm a Korean. If this site provide me service of translate, I need not spend so much time to search dictionary and correct there words again and again(I guess it is the half of my time during using this site) whenever I cannot think proper English words and I want to know the exact mean of your words to prevent my distracting interpretation. I can guess European leaders except England also spend so much time and expense to speak technical terms of English like experts of English. And my nation, China, Japan, and so many other countries excluded your examples still use their mother tongue except English to their official language include debates of parliaments. Of course these countries also concern English very much, but still many people in these countries consider English are still foreign language and such of them also intelligent as compared with many English-users. You said me "the official requirement for translation in the European Parliament causes a great deal of complexity and expense.". But, as I have mentioned before, if you can think this expense, why don't you think the expense of English education around the world include the leaders of European countries? Of course, English is a widely-used language around the world so leaders in the world have to use English at least to some extent. But you also maybe heard specialization in labor. Each people concentrate there best of work and deal with other people, so whole society can maximize the whole wealth. The Best of work for captains of industry well manage there companies. The Best of work for military officers well control there army. The Best of work for scientists well research there subjects. The Best of work for the leaders are not use English well like the experts of English except the leaders of English speaking world. Leaders also can learn English of the level of expert with spending much time and expense, but if industry of translation is far more advanced, many leaders can more concentrate productive work so it can be also benefit of our world include European countries in your example. So I think the huge cost of translation services is, in practice, necessary if the cost of education for technical terms when are using in Parliaments is less than complexity and the expense of your consideration. And the example of bar, also short English users who can only simple chat can use bars. I also think simultaneous interpreters are not needed like the place. We debate to use "technical terms" of English like using international debate. This example is the out of topic in this aspect. And my first suggestion is "Participants of WSDC can be allowed to choose their mother tongue or English.". They also know the importance of English, so I remain the chance of using English by participants of debate. Finally, but if participants of English speaking countries and participants of non-English speaking countries have a similar talent of debate, don't you think participants of non-English speaking countries have a critical disadvantage more than participants of English speaking countries? Your final examples cannot realized easily. Because when participants of English speaking countries need to practice more debate skill, participants of non-English speaking countries must practice more English first. It is not equal conditions. So, at least, participants of non-English speaking countries should be allowed to choose between English and help of simultaneous interpreters.