For anyone else coming here, I'd like to summarize the podcast's relevant points.
When used in direct conversation, it's considered lowly, foreign, or tantamount to 'fighting words'. It is more about just addressing someone without much regard or, at the least, improperly with respect to your relationship, as far as I can tell.
You can, however, use it for translation purposes, for when you require indicating the "you" in the sentence. This comes up in the spoken form when you switch the topic of the sentence and need to directly refer to "you". So in other words there is a specific, but practical use there.
A third use is in writing and music. Music is not directed at anyone, thus saying 당신 is totally fine, encouraged, even, it seems, given how frequent it is. For writing, I understand it as how any language is more specific and more formal when written (99% of the time, anyway), so that would explain why it is allowed.
Another use is between two intimate parties (spouses was the specific example), but it was given with the caveat that it is mostly used by middle-aged and older, giving me the impression that it is a bit more antiquated and proper, but even then it is sort of rare and not incredibly common among all people.
Finally, you can use it as a form of an honorific to refer to someone respectfully in the form of he/she when someone is not there.
So it seems the biggest takeaway here is formality, and context. Use it in the right context, or when writing or translating, use it for your spouse, but don't use it with just anyone, and for those cases, default to 너 if you actually need the pronoun.
Hope this helps!
당신 is usually not used. Unless you're looking for a fight.
But, 당신 can be referred to your spouse as well. So I don't think that this should be removed. And there a few more things that you need to know in using this word.
People who are learning here at Duolingo. :) Please take note that we just need to be careful in using 당신. It doesn't need to be removed from your dictionary.
In English it is normal to use pronouns rather than using the name of the person over and over again. But in Korean, you can use "you" by using the title of the person or the name of the person.
Example using name: 진수 씨 지금 뭐 하고 싶어요? (Jinsoo what do you want to do right now?) You indicate 씨 in every name to sound polite. And if you use this every time in every sentence to say "you", it's okay, it's normal in 한국어.
Example using title: 선생님 이거 뭐여요? ( Teacher, what is this?) There titles such as 아저씨, 아저마, 학생, 엄마, 아빠 etc.
If you don't know the position or title of the person: Omit the subject of your sentence.
I suggest you go learn more about this in "Talk to me in Korean" they have a lesson dedicated to the word 당신 and when and where to use it. I hope this helps!