"виду" isn't in dative case. It's adverb: живут как? - на виду "он/она" isn't omitted: "беспокоящий вас человек" = он/она Nominative case becouse we write about who is speaking. Кто общается? - человек

"жить на виду" close to ~ "to be public" (but 1. is grammatically incorrect / maybe : "Токсичные люди часто живут на виду, (В/НА) поискЕ уязвимых мест и высмеиваниИ других") "с кем из вашего близкого окружения так же близко общается беспокоящий вас человек" -->> "с кем из ваших (друзей/родствеников) человек, который вас беспокоит, общается так же близко (как с кем-то/как с вами)" (당신을 귀찮게하는 사람이 - nominative case)

It is a poor translation from English. The original: https://medium.com/@nyamasensei/how-to-communicate-with-toxic-people-when-you-cant-avoid-communicating-with-them-d617b292816e Interestingly, there is also a back-translation form Russian : https://woman.forumdaily.com/en/kak-obshhatsya-s-toksichnymi-lyudmi-esli-obshheniya-ne-izbezhat/ The English original is also imperfect. E.g. "operational power" seems to be misused:/ As a native speaker I occasionaly had to 'reconstruct' English in my mind to read it comfortably, until I was fed up and just googled it in English:)

2. Держите в голове, с кем из вашего близкого окружения так же близко общается беспокоящий вас человек, и, самое главное, выясните причину их общения: Keep in mind with whom from your close circle the person who is bothering you is also talking closely, and, most importantly, find out the reason for their communication: In Russian you can say both: (A) "С кем общается этот человек" (B) "С кем этот человек общается" Both times "person" is the subject. In this case the translator preferred (A), because "WITH whom" is a part of a construction "to talk with", "общаться с". When "общаться" and "c" are separated by TOO many words it sounds heavy.

1. Токсичные люди часто живут на виду, а поиск уязвимых мест и высмеивание других — их постоянная практика: именно использование информации против тех, кто вызывает негативные чувства, и есть их операционная мощность. Toxic people often live in plain sight, constantly searching for vulnerabilities, ridiculing others is their constant practice: using any available information against those who they dislike, or treat as inferior beings is their operational power. "На виду" means: right before our eyes. "виду" is not Dative. It is Prepositional. Dat: в`иду Prep: о в`иде, на вид`у Some words (~150) have a differert Prepositional case form with в and на (in the sense of location/placement of something "in" or "on" them). We call it "Locative" or "Second Prepositional". Today "вид" is mostly used in meanings: "a kind", "(biological) species", "(beautiful) view/sight". But in "быть на виду" and "иметь в виду" it translates "sight": "a space that is seen or available to be seen". It is the "second prepositional" form. When these idioms entered Russian, such -у forms were more common than today. But: "давайте остановимся на [этом виде] поподробнее" (let's discuss this species in more detail) "в [виде с этого холма] что-то есть" (there is something to/about the view from this hill). 1. Here I inserted вид in constructions "остановиться на [чём-то] поподробнее" and "в [этом] что-то есть". They aren't "fixed expressions" with "вид". They are phrases I created anew. 2. "in" and "on" don't really mean "in" and "on" here! The speaker is not standing atop of a species. There is something "to"/"about" this view as a Whole, not something "within" it. For these two reasons I have no temptation to use "-у". Similarly, we usually say "в доме", "на доме", but in some fixed expressions (like "работа на дому"), in proverbs or when imitating more archaic style we say "в дому". For other words, like "лес" forms like "в лес`у" are still common.