In many parts of the world, many people employ, in the course of their daily lives, two distinct languages. One of these, which might be called the home language, belongs to the country or region in which the people in question live, the other to a broader realm.
In Scandinavia, for example, the home language is Danish, Swedish, or one of the many varieties of Norwegian, while that of the larger world is English. When dealing with local matters, speaking to children, or dealing exclusively with his compatriots, a Scandinavian will use his home language. However, when consulting a shop manual, engaging in trade, or enjoying electronic entertainment, he will switch to English.
Many Scandinavians make such extensive use of English that they speak, read, and write that language fluently. Nonetheless, when expressing themselves in their second language, such alloglots pay more attention to what they are doing than would otherwise be the case. That is, they speak slowly, enunciate clearly, and choose their words deliberately, taking care to avoid slang, jargon, and regionalisms.
Despite such efforts, alloglots face a greater danger of being misunderstood. For that reason, they pay greater attention to the art of listening, watching for nonverbal cues (such as facial expressions) and making extensive use of paraphrasing.
Because of these phenomena, people learning a second language will often find it easier to converse with alloglots than with native speakers. In my own life, for example, my own command of French improved greatly when, while serving in the US Marine Corps, I spent six months working closely with four Moroccan colleagues, one who was also my roommate. (While native speakers of Berber or Arabic, these officers had trained at a military academy where the language of instruction, command, and administration was French.)
More recently, when visiting Montreal, I find that it is easier to speak with immigrants from places recently ruled by France than with native Quebeckers. Indeed, such alloglots are much more likely to compliment my own command of the language of Molière than people with deeper roots in the soil of La Belle Province.
I'm from Gibraltar and like most of us, fully bilingual English/Spanish with neither as a second language as opposed to the Scandinavian example in this very interesting article. From this perspective your point is well made we are difficult to understand for non native speakers of both languages, not least because we flit between both languages mid sentence, but also because when we speak either English or Spanish we tend to dip heavily into truncation of words, colloquialisms, slang etc. As a French speaker to a reasonable standard I also see the flip side of the coin where I will better understand a Moroccan speaking French than I would a native French person. Many thanks for sharing this, language fascinates me
The second-language speakers pay a lot more attention to how and why they say certain words, because they've already passed through the translation filter once. Adding more filtration between brain and mouth catches more inaccuracies.