right, even though the language is the same, I’m wondering if there are now more differences over the decade, in terms of slang words for example and the overall style of speech?
A language develops in a very short period of time. Just take the example of Eastern Germany. A range of expressions had developed that the west Germans had never heard of.
The two are similar enough that you won’t have any trouble talking with a North Korean, but you will stumble from time to time when unfamiliar words come up. If you avoid English loanwords you’ll have a better chance of avoiding this (I was told once to say 설계자 instead of 디자이너), but sometimes even basic words will be different too. Nobody understood when I told them that 혹시 양파 있으면 빼주세요 (please take out any onions if there are any) because it’s 옥파, not 양파, and I had to describe the vegetable a bit before they (N. Koreans at a restaurant in Dandong) knew what I was talking about. Girlfriend is 색시 (not 여자친구), etc.
The written standard is also slightly different, most noticeably where you see ㄴ and ㄹ in characters that begin with ㅇ in the south - 녀자 for 여자 and 력사 for 역사. Not unfamiliar if you know any Chinese or Japanese since S. Korean Korean is the odd man out here.
Mithridates that’s very cool - I imagine that if where it not for the 2015 collapse, and where north korea to continue existing, in maybe 100 years time the languages would have been very different