"K" is almost never neutral. It is a low-effort acknowledgement that closes the conversation instead of continuing it — most often sent when someone feels annoyed, dismissed or too tired to argue. The message is "I heard you and I am done talking", not "yes, sounds good".
The dynamic underneath: Shortening a reply is a form of emotional distancing. By withholding words, the sender withholds warmth — it lowers their own exposure while signalling displeasure without having to name it. Escalating ("why are you being like that?") usually confirms their sense that the conversation is unsafe, so they shorten further.
Replies you can send: Name it gently — "That felt a bit short — are we okay, or did something I said land wrong?" | Give space — "No rush on this. Ping me when you have the headspace and we can pick it up." | Ask directly — "I would rather hear the real version than the short one. What is actually going on?"
Does "K" always mean someone is angry? No. Some people type "K" out of habit or while busy. Read it against their baseline: if they normally write full sentences, the switch to one letter is the signal — not the letter itself.
Should I reply to "K"? Reply once, briefly and without accusation. If the next answer is equally short, stop texting and let the conversation continue in person or later.