I think to be fair, “Letter Format” is traditional, even on forum sites where conventionally like here, you can see all the user information on their profile. Maybe not in our modern internet age, but over a decade ago, it was pretty much the norm for any forum. So there is some historical context that usually bleeds out over time.
Sometimes people will bring back those traditions, especially in a development area where we are expected to be somewhat “professional” at times. No one is doing it for memes (except @lysandr), it’s just a personal way to articulate your message. For example, maybe you would like to include extra information about yourself in a post, or would like to structure your response. Having a random paragraph structure (like I always do) may not be helpful when you are trying to get a point across clearly.
I think it’s also fair to say that everyone has their own style. I like to have one-liners once in a while.
But not everyone is like that, and some people probably don’t like this style. There are one-paragraph walls, 300-page essays, and full encyclopedias you can find all over the forum. That’s what makes this place unique. We are free to express ourselves the way we wish, while still maintaining and upholding a legible style that people can comprehend.
You say there’s at least one topic in letter format when you look at posts - what about the rest? If it was a revived boomer-level trend, I guess it makes sense to bring this up, but from how you described it, there isn’t as much prevalence as you give them credit for.
I like topics like this though, it’s fun seeing how people view the forum and how they feel they should convey themselves on the internet.