On this forum and any other forums you participate in. I imagine for young people who were in their teens/twenties when this forum was created, the changed will be more than for people who were middle aged adults.
I have no style. You should see me dress.
I did a large amount of writing, in my late teens, early 20s working on things like screenplays from classic novels and stories in the style of things like Le Morte D’Arthur and Shakespeare, so that’s effected my writing to be a bit stilted and overly convoluted. I came to the Dope already writing that way.
What the SDMB did was make me hedge on everything. You can never say anything with certainty unless you’re prepared to hunt out a hundred cites in advance and have them ready to drop, which isn’t feasible if you want to have a life outside of posting on message boards, so you have to disclaimer and ambiguate any statement.
In the nearly 20 years I’ve been here I’ve become less combative. I’m told it’s normal to mellow with age. My theory is that you just don’t have as much energy.
Oddly, I was just strolling down memory lane - reading some old 2000’s threads.
I have become much more natural in my writing here, since then. You have to understand that in 2000 the internet was still new, essentially. There was a tentativeness to how to behave, what sort of persona you should present, how much of the lol omg btw smilie culture to immerse yourself in. I read some of my old posts and think, “Christ, what a naive fucking phony.”
However, for the most part, I’ve tightened things up a bit. I don’t abuse punctuation as much as I used to (friggin’ double em-dashes all over the goddamned place). I like to think I’m a little clearer in thought than I used to be. Moreover, I’ve either become much more cynical or I’ve at least allowed my inner cynicism to completely show through. I used to couch every sensitive opinion with a qualifier (“I know this might be a touchy subject but …”). Now I’ve learned to be confident in my opinions - possibly to my detriment.
Throwing tags at the end of my posts, however? Never gave that up.
Terser.
I’m less insecure and defensive now.
Also I make more typos now.
Other than that its the same.
I’ve picked up some proof reading knowledge along the way. But it’s still a drop in the bucket from where I should be.
OTOH, I’m making more goofs than I used to. Brain-deadish all too often. I thought you got better sleep as you got older.
I don’t think I’ve changed a bit. But I do browse differently. I used to only care about GQ and surf on a desktop computer. Now I’m using an iPad so I suspect my spelling has gone out the window.
Right, now I’m going to find some of my earliest posts and see if I’m right.
I’ve been on here since 2004. I don’t think my writing style has changed too much, but with the introduction of mobile, I think most of my responses have gotten shorter. Plus, I’ve worked for the same company for ten year and all message boards are blocked, so most of my responses are on mobile. That also causes more typos, since autocorrect can do weird things and you can’t edit on Tapatalk.
When I first started on here, I was using a desktop and still had a bulky CRT monitor. So, made typing and posting easier.
Of course, with so many years of being on message boards, I’ve gotten much better with thread titles as well as well as putting threads in the proper forum.
I was in journalism school when I joined. I hope I still write as well as I did then!
I, too, only browsed GQ for a long time. I then added MPSIMS and IMHO, and eventually The Pit. I still don’t go in to GD much but now that I use Tapatalk and see “New Posts” I do see GD threads and participate every so often (yes I realize there’s a “New Posts” option in the desktop version but I don’t use it on the desktop).
I’m a blt less argumentative and less sarcastic.
Maybe cleverer too? 
I respond to fewer threads, use less words when I do respond , and will just unsubscribe from a thread as opposed to arguing the endless circles of petty arguments or needless nitpicking of minutiae
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Did you mean to title this, " How HAS your writing style changed? " ??
I’m proofreading now as I did then - I do not believe that my writing style has changed one bit. And I’m a 99er.
I no longer feel compelled to respond to everything related to Tolkien or medicine. And I now seldom bother engaging posters whose postings here make it seem that they have a significant personality disorder.
I don’t think my writing style has changed much at all in the past 15 years. By then, I’d already been a Doper for 4 years, and my current style took shape in my first couple of years as a Doper.
There were two components to this, really. The first was simply the ability to write in a WYSIWYG environment, which gave my words half a chance to keep up with my thoughts. (Back in the days of handwriting and typewriters, the words I was putting on paper would quickly be many paragraphs behind what I was thinking, and I’d just give up in frustration. It was awful.)
And the second was the Dope itself: interesting debates and discussions to join in (which gave me reason to write, and helped me pick up my typing speed), the need to write in a way that other people would be willing to read what I wrote (which pushed me to write with clarity and succinctness), and the awareness that a bunch of very smart, skilled debaters were going to respond to what I wrote (which pushed me away from hand-waving and sloppy logic).
So in multiple ways, the Dope made me what I am as a writer - and believe me, I’m deeply appreciative of that. 
But that largely happened in my first year or two as a Doper, by 2000 or 2001.
In the early 2000’s I started hundreds of threads on this message board, but now it’s been several years since I’ve started a thread here.
I don’t get involved in debates as much as I did when I was younger (feels like too much of an energy drain), but when I do, I would like to think I spend less effort trying to “score points” and more effort trying to actually convince people. It doesn’t work any better, mind you.
I joined here at the invitation of Cecil. I started out as a cynic, mainly to be a bit of a thorn in his hide. One night at dinner before a long tear of drinking, he accused me of being primarily a troll. I took mild offense to his accusation, but stuck that comment in the back of my psyche for the next few years, tried to be more constructive in my posts. Today, he and I only see each other once every few months at social gatherings and the occasional portfolio review. He’s never accused me of trolling since. Even though he can still be a dick every now and then.