I am guessing that adding 능 at the end doesn't really change the meaning or implication much, but there must be some reason why someone would say this instead of just saying 나는 다왔다! or 나는 다왔어!
What is the reason for using this article of speech?
" -다능" 쓰는 이유/목적 뭐일까요?
btw speech is not peach haha
"-다능" just like a part of 'slang'. The word was derived from the Internet, and it just used by very few people (normally, 'otaku').
And so, I think it just fad among people of a certain age. :)
It's part of Korean weaboo language.
You know when English speakers put all those "kawaiiii" comments on Youtube video that has nothing to do with Japan?
It has the same nuance as that.