They can understand the context for employing certain colloquialisms and how to utilize them to express their personality in a second language.
そのサイトの主は 得意のスラッシュリーディングと直訳で次のように解釈しています。
≪They can understand the context/ for employing certain colloquialisms/ and how to utilize them/ to express their personality in a second language.
*context=文脈、背景≒meaning
*colloquialism=ｺろｳｸｨｱﾘｽﾞﾑ=口語的表現、方言
彼らは、5 文脈[→意味]を理解できます/１ ある方言を使用する[←雇用する]ことに対する/2そ して、4どのようにそれらを利用するかに対する 《"for employing"is in apposition (同格）with "(for) how to".》/3 第二言語で彼らの人格（個性）を表現するために。≫
それで、この文で用いられている colloquialismは 次のどれに該当するでしょうか？
① the form of a language that is spoken in one area with grammar, words and pronunciation that may be different from other forms of the same language
② a word or phrase that is used in conversation but not in formal speech or writing
③ a way of pronouncing the words of a language that shows which country, area or social class a person comes from
④ a variety of a language that the members of a particular social class or social group speak
⑤ the level and style of a piece of writing or speech, that is usually appropriate to the situation that it is used in
