I don't know Japanese at all, aside from absorption that lets me skim through reading subtitles much faster because I recognize pattern phrases. My Korean is about the same from watching a lot of movies and dramas: effectively useless. I don't know either of their written languages even on a basic level.
When I said "I've learned from scanlation-drama comments..." I mean the rants that the translators go on to prove they're correct when some asshole was bitching about the translations being "too literal" or "not literal enough" and they go into full details of their transcription processes.