In order to keep in line with our "grand scheme" for Newgrounds, we need to implement new standards for usernames. These are standards we probably should have had from the beginning, as many sites already follow them.
Names that begin or end with a hyphen are no longer valid. You can, however, have a hyphen in the body of your name.
For example, "-SuperJoe-" is no longer valid, but "Super-Joe" is. Double hyphens, such as "Super--Joe" are, however, invalid.
Names can also no longer include underscores, so both names such as "Super_Joe" or "_SuperJoe_" are no longer valid.
From this point on, new account names must follow these rules. Also, you will not be able to edit your user info without being forced to update your name. I know this is an inconvenience for a good number of users, but this change allows us a lot more flexibility with the user system.
We will eventually be "force-updating" names that remain invalid, but for now we are giving users the chance to change their names voluntarily. ALSO, if you are a site contributor, feel free to PM me for preferential treatment. For example, both "-Knox-" and "-Luis-" recently became "Knox" and "Luis", because the original owners of thes names were inactive users who never did anything with their accounts after creating them. I will work with contributing users (such as Flash authors, Audio Portal contributors, high ranking users) to give them the best names possible.
Sorry again for the inconvenience, and thank you to everyone who voluntarily makes the transition!