What does 있어서는 안 되는데. mean?

Question

What does 있어서는 안 되는데. mean? For full context the content is:

석진: 그래서, 오늘 경은 누나가 오늘 회사를 안 나왔죠?

현우: 사실은 회사에 오다가 아파서 다시 집으로 돌아갔어요. 이런 안타까운 일이. 있어서는 안 되는데. 지금 아파요. 많이 아파요. 그래서 이 주제를 생각하게 됐어요. 건강이 정말 중요한데, 석진 씨는 건강을 어떻게 유지하세요?

I saw "있어서는" can be used in the idiomatic expression meaning "when it comes to", but I don't think that is the case here. https://korean.stackexchange.com/a/3180/3019

My interpretation is "있어서는 안 되는데" means that the the lady Kyung-in should not stay at the office and instead should go home. What leads to my confusion is that 는 is a topic marker but it is placed after the phrase 있어서, which means "because it exists", but instead I would a noun or pronoun to precede 는 like 저는 (I).

I've asked too on hinative, but am still awaiting a satisfactory answer. https://hinative.com/en-US/questions/17103129

Answer 1

When 있어서 is used as an idiom for "when it comes to" or "as it relates to", its full form is -에 있어서(는) and it should be followed by some descriptive statement, not 안 되다.

V-아/어서는 안 되다 may be considered another idiom which is equivalent to V-(으)면 안 되다 ([you/they/it] V-ing will not do => [you/they/it] should not V).

는 in this case is an auxiliary particle that attaches to another particle for emphasis. It kind of wraps the phrase and says something about it more categorically.

So 있어서는 안 된다 is literally "it should not happen" and conveys the speaker's sentiment of not wanting to see such an event happen, which in this case is the person 경은 falling seriously ill.

The sentence 이런 안타까운 일이(.) 있어서는 안 되는데 (the period after 일이 might be a typo as it reads better without it) means "There shouldn't be such a sad/deplorable thing" (i.e. the speaker feels bad about it), or "It's a shame such a sad thing happened", where the "thing" is the fact she fell ill.

Other examples.

• 모르는 사람이 같이 가자고 해도 따라가서는 안 돼. (Never follow a stranger even if they tell you to come with them)
• 사회의 질서를 위해 이 같은 일이 허용돼서는 안 된다. (For the order of the society, this kind of things should not be tolerated)

Answer 2

있어서는 comes from 있다 meaning something happening.

verb + ~해서는 안된다 is typical expression to mean you shouldn't do something. 있어서는 안된다 therefore means something shouldn't happen or shouldn't have happened.