Can I say なるほど when talking with customers?


I was told in class by a Japanese teacher that なるほど can not be used when
talking with people above, but in the same lesson we listened to a CD
(training material) where a student was saying なるほど to his teacher.

Here at work I often hear my Japanese colleagues saying なるほど when talking with
customers (consulting). Can I do the same?

**EDIT** : A Japanese friend just told me she would never write it to a
customer, even by email, but it is perfectly acceptable over the phone as an
相槌 (sound given during a conversation to indicate comprehension).




Technically speaking, なるほど is something of a casual/frank word. However, it
seems that [native
speakers](http://komachi.yomiuri.co.jp/t/2010/0614/323211.htm) can be confused
as well, and there are plenty of people who use it anyway in business
settings. Apparently it's not a particularly noticeable faux pas, but one to
be avoided. Some of the commenters in that thread suggest replacing it with
something like (depending on context) 「かしこまりました。」or「そうでしたか。」.




Technically speaking, なるほど is something of a casual/frank word. However, it
seems that [native
speakers](http://komachi.yomiuri.co.jp/t/2010/0614/323211.htm) can be confused
as well, and there are plenty of people who use it anyway in business
settings. Apparently it's not a particularly noticeable faux pas, but one to
be avoided. Some of the commenters in that thread suggest replacing it with
something like (depending on context) 「かしこまりました。」or「そうでしたか。」.

