This isn't the first time but sometimes when I'm reading KR MTL, for whatever reason there will be words like "senpai", "sama", "chan", even though it's clearly a KR novel. I don't know why this happens since KR has their own honorifics...
It's weeb culture, sometimes you will see japanese name with korean surname in characters affiliated to the mafia as well. It happens in chinese novels too.
I don’t know if you’ll call them actual translators since it’s literally MTL but it’s still strange that that would come out in TL. Like, whether it is just the translating app or the guy MTLing it, it’s still weird, especially since it seems cleaned up in formatting, so why not clean that part up at least. This isn’t even on one website, I’ve seen this happen on different sites, although I can’t remember which ones. I’ve MTLed myself before and this has never happened, so I’m inclined to believe that the editor/cleaner did it but it’s so strange. Just because people are more likely to be familiar with JP honorifics doesn’t mean there aren’t plenty of people familiar with KR terms... (BTW this thread literally has zero profile pics and I don’t know how to feel about lol)