Display Name Change?

Is there a way to change my "Display Name" to something else rather than my actual Username? I tried the "Real Name" field on the Wiki Preferences page but it gives me this error message when I try to change anything, even my time settings:
"There was either an authentication database error or you are not allowed to update your external account."
Also, we do get to choose a separate name for our character than our Username correct? I'm pretty sure on this but would just like some confirmation. And do we get to have one character at a time or multiple characters at once?
Thanks.
Three characters per account
Account name and character name(s) do not need to match

Thanks for the replies so far.
And by Display Name I mean, for example, are Pupa and BehindCurtai your actual Usernames (you log in with) or separate "Display" names you chose on some form I have not yet found/cannot access?
You account name is currently set as you forum/wiki name.

Pupa and BehindCurtai are their actual usernames that they log in with. :)
"BehindCurtai" (the "n" is missing because of length limits) is my account name. That's what I use to log into the game or the forum. It is known to people who have played YPP.
I have two different characters, both with different names. One primary explorer that has just started to switch to equipment better than the starting stuff, and one that just lurks in the arcade taking notes on gates.
This forum doesn't have a concept of signatures, separate account name from full name, etc. It is just a bare bones message thread collection.

Alright I see, it makes sense to me now. Thanks for the clarification everyone.
Yes, there should be a "screen name" for the forums wiki.
But I guess it's not priority for the devs right now.
And yes, names for characters can be chosen.