例の英語の「同じ単語を一つの文章の中で繰り返さない」という暗黙のルールですが、ネットで調べた限りでは、このルールは元々フランス語のもののようです。ご承知の通り、中世ではイギリスとフランスは同じ王によって治められ、多数のフランス語の語彙が英語に流入している訳ですが、当然上流階級が話す言葉がフランス語であれば、英語にもフランス語の慣習が持ち込まれても何の不思議もありません。
つまりこのルールには最初から一種の鼻持ちならない階級意識みたいなものが随伴していると言えそうです。
他のイタリア語やドイツ語などでは、相手の疑問文中に出てくる単語を、答えの中では代名詞で置き換えるというのは非常によくあります。ですが、英語みたいに名詞を同じ意味の名詞で置き換えるなんてことは、私の知る限りほとんど出てこないですし、ドイツ語で卒論を書いた時にもドイツ人教師（複数）からそういう指導は一切ありませんでした。またドイツ語やイタリア語では名詞に性があり、代名詞もその性に合わせて語形が決まり、どの単語を指しているかの判定が比較的容易です。しかし英語の場合は人間を指している場合を除いて、名詞の性は明確ではないので、代名詞による判定は簡単ではありません。（例外的に、例えば船については女性扱いでsheで受けるとかありますが。原子力潜水艦シービュー号でも、シービュー号は常にshe/herと女性扱いで参照されています。例えばTake her up!は潜水艦を浮上させろ、という意味です。）
Eigoxの先生に聞いた所によると、通常の生活で使う語彙は高校までに習得するもので十分で、TimeやNewsweekやNew York Timesで使われる日常ではまず見ない奇妙な語彙は、基本的に大学に入る上でマスターしないといけないということみたいです。なのでネイティブも私が買ったような語彙増強本を買って必死に勉強して、やっとこれらの雑誌や新聞の語彙が理解出来るようになる訳です。私が何度も経験したのは、この手の雑誌や新聞に出てくる聞いたこともないような単語を辞書で調べてみると、多くは単純な意味に過ぎず他の単語で表現することが可能です。にも関わらずそういう語彙を使う一つの大きな理由として、この「同一単語の繰り返しを嫌う」慣習から来ているケースが多いということです。これらの語彙を知っているのは「大学で学んだインテリの証拠」ということになり、ここにもまたある種の特権意識が見られます。
私は「同じ単語を繰り返さない」というルールについては、メリットとしては、微妙な意味合いを持つ概念を複数の言葉で描写して、その意味を分かりやすくさせる、小説などで読者を退屈させないようにする、ぐらいしか見つけられません。逆にデメリットは沢山あり、まず契約書や技術的文書のような曖昧さを嫌う文書ではまず適用出来ないというのが挙げられます。また言うまでもなく、文章の意味を曖昧にしかつ意味が明確に伝わるのを邪魔します。更には文章を書くのに余計な時間がかかります。（英語のシソーラスはほとんどこの目的で使われていると言っても言い過ぎではないと思います。）私はウィリアム･ストランク･Jrの”The Elements of Style”を持っていますが、このライティングの古典的教科書が言っていることは、「簡潔で、明確で、力強い文章を書きなさい」ということで、同単語反復禁止ルールはまさにその反対のことをやることだと思います。

The following is my essay that I wrote as an assignment for an English school AEON:

Topic: What are your thoughts about the Japanese youth culture?
Style: Formal

Regarding the Japanese youth culture, the most important buzzword to describe it might be “otaku”. The Japanese word “otaku” is usually translated into English as “geek” or “nerd”. It is often alleged, however, each of them does not exactly reflect the true meaning of the original Japanese jargon.
The word “otaku” appeared first in some print media in the early 1980’s. It was almost the same time when many sub cultures became viral, especially comics and animations. Otaku, in the first place, was used to describe young people who are too enthusiastic about comics or animations. The original meaning of otaku in Japanese is a vocative expression of second person. The word is used for those who often try to talk to others starting with ”hey, otaku”.
Comics were popular even before World War II and the first TV animation started in Japan in 1963. After the tremendous success of an animation movie Space Battleship Yamato in 1977, the number of young fans of comics and animation skyrocketed and both genres became big industries. The word otaku appeared around this time.
At the first stage, the expression contained a rather negative connotation as they have interests only in virtual things and do not have much contact with the real world. This negative image was exacerbated when the Tsutomu Miyazaki incident happed in 1988 and in 1989. The criminal was 26 – 27 years old at that time and killed four female children aged from 4 to 7. By the investigation of the Japanese police, it was revealed that he was holding more than 5,000 video tapes of animation or drama. Most people related the image of otaku to him.
The image of otaku was gradually improved during the 1990’s and in some case the expression was used to describe somebody who has some sophisticated knowledge for something. The areas of interest did not stay only at comics or animation, but they spread to many genres such as computer, train, military, movie, Sci-Fi novels, camera, audio, and almost all sub cultures.
Currently, it is argued that otaku culture in Japan declined a lot while the Japanese government is bubbling over promoting otaku culture to foreign countries with a disgraceful copy “cool Japan”. (Who dares to say “I’m cool!”?) The main reason might be bad economical status of the younger generation.

The following essay is what I wrote as an assignment of an English school AEON.

Topic: Cell phones and social etiquette
Style: Formal
Among many alleged manners for cell phones or smartphones, the most vocal one in these days might be “do not use your cellphone/smartphone while you are walking on the street”. It is absolutely true that looking at the screen of a cellphone/smartphone during your walk is quite dangerous not only for you, but also for others whom you may jostle. Some of smartphone applications, however, require users to watch the screen while they are walking. The most typical one is Google Map. Many people (including myself) use the app to find destinations when they are lost in unfamiliar areas. Some may argue that we should use the “vocal guidance” function so that we do not need to look at the screen. For many others, however, it is inevitable to look at the screen even with some vocal guidance since the app is named “map”. And a map is to look at while we are walking. In the past, when we had no cellphone/smartphone, nobody said that we should not look at a paper map while we were walking. The difference between the old information system and the new one is, just the number of people who use it. People did not always have maps in the past, but now most of them have smartphones and they use them almost all the time while they are awake.
From this example, we can argue that we should think more how to solve the addiction to smartphone than to expect good manners for smartphones. For many young people, the first thing to see in the morning after they woke up and the last thing to see before they fell asleep are the same thing, their smartphones. When I travelled in China in last September, what shook me most was the fact that many young engineers with whom I had a lunch one day started to check their smartphones as soon as they finished eating. At this point of change in personal behavior, we should intensively study potentially negative impacts to human health for both body and mind.
As a conclusion, smartphone addiction is quite a serious problem and to consider good smartphone etiquettes is quite useless without thinking of possible solutions for this addiction.