let me tell you the origin of that word "꼴값" '값' is from "Value(Price)" (examples: 몸값, 밥값) '꼴' is originated from "값" and its meaning is 'The shape of an object' or '(disparaging) The appearance of someone.' (examples: 꼴사납다, 꼴좋다)
therefore, 꼴값하다 is "(disparaging) to conduct becoming to one's appearance" and this is a negative word(It's not good for formal place)
꼴값떨다 is more negative expression of 꼴값하다(꼴값한다) because 떨다 is "to repeat a certain act lightly and carelessly." 꼴값떨고있네 and 꼴값떨다 have same meaning , but the former is conjugational form and more casual conversation
꼴값떤다, 꼴값한다, 꼴값떨고 있네 are all the same in meaning "f**king nasty". It originally meant "doing like one's appearance is", which is an insulting phrase by likening one's excessive behavior to the person's appearance. It's a kind of raw expression of hatred toward someone.
@popularity@pt707 Oh. A Korean person had asked how to say this in English and I didn't know, so I decided to ask another Korean person who speaks English better than I speak Korean to translate it for me. I apologize for asking about cusswords. I wouldn't have asked about them if I knew it was that phrase. You did teach me something I didn't know though, so thank you both.
@LilChee Thank you for sharing the background in detail. The Korean phrase you asked reminds me of the story of "The Ugly Duckling". The duckling's siblings made fun of him and treated him horribly because he didn't look nice. The nuance of the phrase 꼴값떨고 있네 is similar to what the siblings told the duckling. So the meaning of 꼴값떨고 있네 is more like "You're doing it, because your appearance is so ugly and nasty" or "Your appearance tells why you're doing like that".
I guess the Korean asked you about it purely out of curiosity because the person might not find a matching idiomatic phrase in English. I would also ask you about a similar idiomatic English phrase. In this regard, I don't think you did wrong when you asked another Korean person for the translation. (I sense your humbleness by your saying of your apology.) Inquisitiveness generates questions, and the question motivates us to learn, right? I think we can ask whatever questions when it comes to language or culture.