1. Must represent a single person, not a company, organization, website, band, partnership, or other group of people
2. Must not be deceptive or impersonate someone else
3. Must not be unreasonably long
4. Must not be inflammatory or imply that you intend to troll
If you create an account that doesn't meet this policy, an administrator will prevent you from editing until you choose a new username, and you can continue afterward.
https://en.wikipedia.org/wiki/Wikipedia:Username_policy
You're absolutely right in that Wikipedia needs to improve its user experience to ensure that new editors know what the rules are before they accidentally violate them.
It's repeated for every single policy page - they are enormously long and complex for every single topic. There is nothing remotely like a friendly beginners guide to helping - be that fixing some poor language, or correcting a mistake. You have to plough through the meta Wikipedia policy encyclopedia and figure out what's relevant or not the hard way.
On my experience many moons ago, Wikipedia was one of the most hostile sites I've ever encountered for new users. I dread to think how a subject expert who isn't also an IT expert finds it.
No, an admin may instantly block you permanently, or may temporarily block you until you change your name, or may temporarily block you while they discuss it with you, or may not block you but apply one of two templates, or add your name to a username for discussion board where you'll have to try to justify your name.
EDIT: Reads some stuff about his company. He knows that information is factually incorrect. It's not harmful to his company, but it is misleading to people reading Wikipedia. He signs up for an account.
If he signs up a "xargleblarg" he's fine, he can edit the article.
If he choses to be open and honest and he signs up as "Bob from BobCo" he faces instant blocks across multiple policies (COI, Spam, spam username), even if those policies are being incorrectly applied.
> This page in a nutshell: When choosing an account name, do not choose names which may be offensive, misleading, disruptive, or promotional. In general, one username should represent one person.
Seems fine to have the sussinct description at the top followed by details on the same page. If there really are lots of people that have issues picking a username (these policies seem petty typical so I’d expect most users to be fine) then a link from the create account page would be a good idea.
For a few years the new username lists were trawled by vandal patrols and there was a lot of biting of newbies -- so much that "don't bite the newbies" had to be added to the policy pages.
For example: the section on "confusing usernames". This was added to avoid people suggesting they were a bot account if they weren't a bot account, or were an admin if they weren't an admin, or to prevent impersonation.
So, if you register as "kjwenflkjclnaksdnalmsd" that's confusing, but it's not against the policy. Except a lot of people reporting usernames hadn't bothered to read the policy, and so they were just reporting names like that as confusing. For sometime people using their real names in a non-latin script were being blocked because their name was "confusing". This again led to changes in policy.
What WP really needs to do (and what they've actually done) is have a bot that checks usernames and places them on a list with descriptions of the problems, and warnings about why it might not be a problem. (There are differences between "WhitePower88" and "MartyJenkins88") -- and then have people checking the list.
The only interactions I had with Wikipedia are reading articles. Even I know it is frowned upon to edit your own articles.