This is 100% old-man energy, but I dipped back over to reddit after a week or so and man did I forget how many completely random acronyms get thrown around there... FW, TIL, ELI5, FWIW, IANAL...
Don't even get me started on ETA, which should mean "estimated time of arrival", but has instead been used to mean "edit to add", even though just putting EDIT means the same thing??
I see that kind of stuff a lot less here, and I'm assuming it's a mix of older audience and smaller user base, but so far it's been so much nicer actually understanding what everyone is saying here.
The Internet's always had a lot of acronyms, though. Hell, pretty much anything with a technical bent to it does. I'm currently learning ham radio and there are a large variety of three letter "Q codes" used to indicate anything from "your gain is too high" to "switch frequencies". Yeah, Reddit's going to grow its own acronyms, and that's okay.
Honestly, it's like Kleenex versus tissue paper. Maybe one is more on brand, but everyone knows exactly what you mean either way.
My intuition tells me that a direct message is a message directly to my username inbox, and a private message is basically the same thing but maybe encrypted or something.
I have never heard of ETA meaning edit to add. I'm guessing FW means forward, I'm not sure if I've actually seen fwiw, and I think people just like IANAL because it has the word anal in it.
I agree with you on the til and eli5. I've seen these terms seeping out of Reddit as well.
One thing that made me honestly irrationally angry or somewhat disgusted is people saying happy cake day, and flopping their stupid emoji in there. My Reddit account was like 13 years old, and I never felt like I was missing anything there.
Believe it or not, the context in which I saw FW, the person meant "fuck with". It was a comment about a tattoo, and their response was "Honestly, I kinda fw it."