check this link - <a href="http://www.koreanwikiproject.com/wiki/index.php?title=Internet_and_text_messaging">Internet and text messaging</a>: Adding ㅇ as the final consonant (받침) --> when there is no final consonant (받침), some people add a ㅇ to make it sound more cute. This is usually for the final word in a sentence or clause. Substitutes for the 요 ending --> sometimes using the respectful ending 요 with someone too much can make the conversation seem less casual, especially if the people are around the same age. So in order to make the conversation seem more casual without reverting to 반말, people will often use other forms of 요. Some people also use these 요 substitutes just for fun even to their close friends. Alternatives for 요: 여 염 (여 + ㅁ) 용 (요 + ㅇ) 욤 (요 + ㅁ) 욘 (요 + ㄴ) 효 however, having read the answer of Min, I can't tell whether it's the use of this very word (멋있졍) or of the endings 여 and ㅇ in general makes one sound as an idiot - I'm not that far in my language learning so I just don't use these endings by myself )) hope it was helpful ~~

I recommend you don't use it. It sounds that the person who uses that word is an IDIOT. You can say 멋있죠? 멋있지요? to the older people, or 멋있지? to the younger.