Navigating the comment section of an article is difficult to navigate. The conversation often goes wildly off-topic, the commenters are sometimes hostile, and the environment can turn at a moment's notice. To make it worse, people have a unique short-hand for communicating, making the actual comment hard to decipher.
Allow me to help you.
"First" or "1st" or anything translating to first is an obnoxious comment left to indicate that the commenter is the first to comment. This is really annoying and almost never includes additional commentary. This is always frowned upon, and often banned or frowned upon.
IA I Agree
MTE My Thoughts Exactly
OP Original Poster
TLDR or tld;r stands for "too long; didn't read." This is also advised against as it is also posted alone, and while one may interpret it as a necessary way to let the author know that
Vocabulary Lesson: Web Jargon and Internet Slang (Abbreviations)