I am frequently amazed when I see someone I would swear I have never seen post before and I click on their Avatar to see when they joined and learn they have been here for decades. And not someone who gets the little Discord notice that this person has not posted in a while. A regular contributor.
I will not name names mainly because I do not want to embarrass myself more than I already have.
Am I the only one who experiences this?
(Just curious)
I do this routinely.
I am not good with name recognition in real life to begin with.
Less so with online name recognition.
Although some of y’all do stick in my mind 
Discourse
Oops… 
Welcome to the Straight Dope Message Board, @Whack-a-Mole! What a great idea for a first post. I hope you’ll stick around!
Yes ! I have frequently seen this and intended to find someplace to
remark on it. And that place is here !
Lotta folks seem to live in only 1 or 2 categories. If those aren’t categories you frequent, it’s only when one or the other of you venture outside your neighborhoods that you possibly cross paths.
It happens to me often, more lately for some reason.
I’m probably that poster. Sorry everyone!
Like natureboy, who got banned this morning; I’ve pretty much steered clear of all political threads since the election, note. Thing is that is a common nickname for me courtesy of my friends and family. I saw the notification and immediately went, “Who?”
On the hamburger menu there’s a [Users] choice. If you tap that you’ll get a roster of users active in the last week. Which you can sort by post count to see the busy ones. You can learn a surprising amount of stuff fiddling w the scoping & sorting options on that page.
What’s amazing to me is some of the most vociferous posters are folks whose posts I almost never see. Why? Different categories mostly.
ETA: That display is vastly more readable as a table on a tablet or larger screen vs near useless as a list of fact-boxes on a phone.
There is a hamburger menu! How interesting!
I’m Whack-a-Mole and this is my favorite message board on the internet.
(hat tip to Mass Effect and Commander Shepard)
Yeah, I clicked on the “Users” link for the first time out of curiosity. There were a few people I didn’t recognize because they’ve never posted anything (so duh) then I looked at a couple others who are even Charter Members I didn’t know. I wanted to see where they were active and… No wonder. Topics I’d never be interested in, like thread games or a thread just called, “How are you?”
On a tablet or larger, not a phone …
By default the sort is you first, then posters in most-recent post timestamp order. Which is rather useless. But if you click the “replies posted” header it’ll re-sort to you first, then the rest of the board with the verbal diarrhea crew first and the 1-post-per-week crowd last.
I don’t really recognize one of the top 10 posters. The name is vaguely familiar, but I have no mental picture of anything they’ve ever said. The only place I have ever seen them may well be on that users list.
Yes, I am regularly surprised to see a new harcore lurker pop out of seemingly nowhere. It’s a thing.
You’re #1 on that list. #5 is knoodler, which may be the same poster you’ve never seen. The name rings no bells. I checked and every post is in Thread Games.
The Games forums feel like a different world from CS and P&E.
But the OP’s question is not about lurkers you’ve not seen. It’s about frequent posters you’ve not seen.
Discourse calls out the lurkers for us with at special banner about “@SoAndSo hasn’t posted in X months / years. Welcome back!” This is about the posters who don’t get that banner. Meaning they’re regulars, but ones you don’t recognize.
Honestly…yeah. Or close. I do recognize you but barely.
To be perfectly clear, that is a me problem (really, not kidding at all). You keep doing you!
Sometimes people change their names. Tuba use to do it when asked; I don’t know what the policy is now.