TL;DR

A: TL;DR - We think we figured out which member of the group it was and have his twitter

Too Long; Didn't Read. 의 줄임말로, 어떤 길 글을 알려주고 글이 기니까 내가 요약해줄께. 정도의 의미로 사용하면 될 것 같습니다. Urban Dictionary 에도 아래와 같이 나와 있네요.

A) "Too long; didn't read.", meaning a post, article, or anything with words was too long, and whoever used the phrase didn't read it for that reason. 

B) Also used by someone who wrote a large posts/article/whatever to show a brief summary of their post as it might be too long.

a) 

Source: https://www.urbandictionary.com/define.php?term=tl%3Bdr