It was useful for asking questions that neither you nor the other person would want to put in a public post. For example, someone posted a picture in the bad real estate sub that looked very familiar, and I sent a DM asking “is this X location?”. I might not want people to know I’m familiar with X location, they might not want people to know they’re familiar with X location, but maybe we’re both ok with each other knowing.

But I’m pretty sure its main use was sending hate to people without getting banned.

The author says almost exactly the same thing at the end. Maybe it should have been at the beginning.

Or puzzles that are completely esoteric or unintuitive. Just replayed some of the Myst games, and it’s like “oh ok I was stuck on this for 30min because the lever was on the other side of the map and there was literally no indication that it was related”. That’s just artificially inflating your game’s difficulty, and it’s lazy puzzle making. Boooo