There is no doubt that many "speakers have many times decided to use a phrase in Mandarin to convey their ideas without any translations" (Don't forget about non-Mandarin speakers, by Mrs A. Staveley-Taylor; Aug 27).
However, we have to look at issues like these objectively and take the context into consideration.
Take, for example, during a lecture when a professor experiences some difficulty in explaining or expressing certain ideas. This leads to him switching to his native tongue, which most people find comfort in.
In universities, students come from all over the world with their own native languages; even the English language can be complicated for them to master.
Should the professor then translate whatever he says into the native languages of all his students? That would be exceedingly impractical.
One reason why a professor may attempt to explain a concept in Mandarin when he cannot do so in English is that, as the Chinese are the racial majority in Singapore, this will mean that more of the class will understand his explanation. I do not think anyone should have to apologise for that.
Students, whether or not they are able to understand or speak Mandarin, should take the initiative to consult the professor to clarify their doubts.
However, I do concede that certain speakers do not clarify what they said in Mandarin, and they should open the floor for students to clear their doubts.
Julian Lai Jang Ein