AFAICR: As Far As I Can Recall
AFAICT: As Far As I Can Tell
AFAIK: As Far As I Know - meaning to the best of your knowledge
AMA: Ask Me Anything - meaning an invitation to ask the person a freeform series of questions
BOFH: Bastard Operator From Hell
CCW: Comments and Criticism Welcome or Constructive Criticism Welcome - meaning an invitation to critique the persons work for improvement purposes
CMM and CMV: Change My Mind or Change My View - meaning an invitation to convince the person that they are wrong or perhaps there is a better way
Cake Day is the anniversary of the day a user signed-up for or otherwise joined a service
DAE: Does Anyone Else - meaning a question to see if other people agree
DILLIGAF: Do I Look Like I Give A F-ck?
ELI5: Explain Like I'm 5 (years old) - meaning to explain something in less technical or in layman's terms for easier understanding of the subject or concept
FIFY and FTFY: Fixed It For You or Fixed That For You - meaning that the reply contains a quote that has a portion changed for correctness, clarity or possibly humorous affect
FOMO: Fear Of Missing Out
FSCK: File System Consistency checK - is a system utility for Unix-like operating systems. It is sometimes used as a replacement for "f-ck" in technical conversations
FUBAR: F-cked Up Beyond All Recognition
FWIW: For What It's Worth
FWP: First World Problems - meaning a relatively trivial or minor problem or frustration in comparison to the bigger picture or a larger group of those it affects
GTFO: Get The F-ck Out
H/T: See, "Hat-tip"
HAND: Have A Nice Day!
HITL: Human In The Loop - meaning that whenever possible, keep a human perspective and approval for any output performed by automation
HMB: Hold My Beer - meaning that the person is probably going to try something knowingly foolish or troublesome
HTH: Hope This Helps
Hat-tip: A reference to or gives kudos to were the source of information originally came from
Hugged to Death: A website or service that is inaccessible due to overwhelming traffic coming from a wave of current interest
IANAD: I Am Not A Doctor
IANAL: I Am Not A Lawyer
ICYMI: In Case You Missed It
IIRC: If I Recall Correctly
IMO, IMHO, IMNSHO: In My Opinion, In My Humble/Honest Opinion, and In My Not So Humble Opinion
IOW: In Other Words
IRL: In Real Life - meaning how something actually works in practice as apposed to theorized on paper
IYKYK: If You Know, You Know - meaning that it doesn't need to be explained if it relates to you, otherwise it likely doesn't
J represents the smiley face emoticon emoji in the Wingdings font family. If you don't have Wingdings installed, or the font formatting is otherwise lost, a capital J will be present in the text
J/K: Just Kidding or otherwise joking
KYC: Know Your Customer - meaning that access to your services should require a registration and preferably a login of some sort
KYS: Kill Your Self - a common insult amongst irate online communications
LOL: Laugh Out Loud
Lurker is a user who reads posted content but rarely or never makes public posts or replies
Mod: Moderator - a volunteer who helps run a community
NSFL or NSFW: Not Safe For Life or Not Safe For Work - Typically used as a warning that the content should not be opened or viewed at work or in front of children
OC: Original Content - meaning the author of the post created the content shown or linked to in the post
OP: Original Poster - meaning the author of the post, or the top level comment in a comment chain being replied to
OT: Off-Topic - meaning that the post or statements are knowingly not the primary topic where the post is taking place, making it easier for some people to ignore the post completely
PFY: Pimply-Faced Youth - meaning a junior coworker or subordinate
PHB: Pointy-Haired Boss
PICNIC: Problem In Chair, Not In Computer
PSA: Public Service Announcement
RTM or RTFM: Read The Manual or Read The F-cking Manual
Repost: is content that has already been posted or submitted
SMH: Shaking My Head
SNAFU: Situation Normal, All F-cked Up
SO: Significant Other
STFW: Search The F-cking Web
Slashdotted: See, "Hugged to Death"
TARFU: Things Are Really F-cked Up
TIFU: Today I F-cked Up
TIL: Today I Learned
TL;DR: Too Long; Didn't Read. Sometimes used as a synonym for summary
WIP: Work In Progress
X-Post: Cross-Post - meaning a repost of something currently and actively posted on a different list or community for additional exposure
YMMV: Your Mileage May Vary
YSK: You Should Know
ಠ_ಠ is an emoticon that indicates disapproval
-`ღ´- is an emoticon that indicates lots of love
/S: Sarcasm - meaning that the associated statements are meant to be sarcastic - just in-case that isn't clear to the reader
/Thread: End-Thread - meaning that this should be the end of a reply thread. That nothing else can be added to improve upon or top what has already been said