I keep a whole folder on my phone for quick chat horror. The ones that truly get me are the ones where the mundane platform is the threat—like a group chat where one member insists they never sent that last message, or a customer service bot that starts giving eerily personal advice. A classic that still holds up is 'The Neverglade Mysteries' by Brian Martinez, which plays out as a series of forum posts and DMs. The formatting pulls you right in, and you can read it in one sitting.
What elevates these for me is the subtle wrongness that creeps in, not the big jump scares. A time stamp being off by a decade, a profile picture changing to something impossible, the 'seen' receipt appearing under a message from a deleted account. That stuff lingers because it feels plausible. My personal barometer is if I find myself side-eyeing my own notifications afterwards, then it’s done its job.