Because it creates a new identity. The only way anyone on HN can recognize you is your username. Changing it at will would allow anyone to shed their identity on HN at any time while keeping the karma and account privileges they've accumulated.
Perhaps that is something that's worth allowing, and iirc dang et al have made some vague statements that they may be interested in allowing that at some point, but the ramifications would be substantial. This isn't something that should be taken lightly, nor should it be expected/implicit that a social site will accommodate new identities on-demand.
My anonymous (to everyone but the NSA) username will be a different anonymous username. The karma/privileges are entirely dependent on the quality of my posts, not some inherent value of the username. Also the posts that generated that karma would still be there under the new username.
I'm not too concerned either way , but I don't see why that would be a big deal.
Again, identity. You're not anonymous here, you're pseudonymous. Believe it or not, but I do actually recognize a lot of people here by their HN usernames, and I would mind if those were to randomly change all the time.
Anyway, I suspect that if you e-mail HN mods, they could be able to correct your username in no time. But making it any easier than that would, IMO, be harmful to community.
What is the abuse? Changing your meaningless identifier?
Despite your explanation, I still don't see any actual damage. I made up the identifier in the first place. Why should anyone care if I change it? All my posts will remain my posts.
The only thing is that maybe some people who remember my posts with the old username won't recognize the new name as the same poster, which I don't see as a significant issue. Is that a problem for forum managers? I would have thought they would have problems with people creating multiple new accounts and spamming, not changing the username of existing accounts.
> who remember my posts with the old username won't recognize the new name as the same poster, which I don't see as a significant issue. Is that a problem for forum managers?
Yes, because people will abuse it. If you keep track of violations (especially in moderated forums) it's important to know who did what. And while your primary key on the DB might still be the same, people don't know it, they know your nickname.
Some people would change it every time they comment just for the sake of it
New account creations have some kind of gatekeeping/email verification so it's not as efficient, and admins have ways of checking if this was done with the purpose of evading a ban for example
But if you want to change it because you made a typo or for a similar reason admins usually let you do it (they have to change it for you though)
That can be addressed within the UI. E.g. display the old name next to the new name for a few weeks. After that, just leave a symbol indicating that this username has a change history, which could be presented on click or hover.
Perhaps that is something that's worth allowing, and iirc dang et al have made some vague statements that they may be interested in allowing that at some point, but the ramifications would be substantial. This isn't something that should be taken lightly, nor should it be expected/implicit that a social site will accommodate new identities on-demand.