Members help other members with technical questions and problems using Writing.Com!
The copyright notice on your items is a recognition or acknowledgement that you hold the copyright and have given the site permission to show it to other people. It's the same as when a printed book shows a copyright notice. It's informational only --- it tells readers that this material has a copyright, who holds it, and that it is not in the public domain.
The notice lists both your username and handle. If someone wishes to contact you about your copyright, they can email you at your wdc email address. Your account privacy is maintained.
The copyright notice on your items isn't an official copyright granted by the copyright office. An official copyright notice is something you would pursue once a work is finished and published. If you want one of those, you have to fill out the paperwork and submit the fees to the official copyright office yourself, or if published by a publisher, they handle it.
Since this site is not a publisher and is intended for works in progress, the informational notice of the automatic copyright the author has from creating the work in a fixed form, is considered sufficient for the situation.
If you needed to prove copyright for court proceedings, you would use your original manuscript or files to prove you'd written it. Or you'd use your official copyright documents if you had them. Since your items here are editable, all that the copies here could add would be the last modified date on your item, which might not be useful. If necessary, you'd prove you were Duhhfactor by demonstrating to the court that it's your account.
If you changed your username to your real name, yes, it would affect your log-in. And other things.
Hope that helps.