Although the filed looks editable when you choose Edit detalis it is not possible to change the username. The manual says it can be done but it is not possible in our instance of Confluence Ondemand.
Without more details from what is happening, I suspect you'll need the help of Atlassian support engineers. Try logging a ticket for this at https://support.atlassian.comunder the Confluence OnDemand project.
UPDATE: I've been informed it is not possible to change usernames in OnDemand :)
It is possible in the locally installed distribution of Confluence, so you may have been looking at that particular documentation.
It appears that the question asker (Torsten) was repeatedly accepting and un-accepting the correct answer, over and over again, and causing an email notification to be sent each time.
I have temporarily suspended Torsten's account in the hopes that it will stop it from happening.
I suspect the same thing is happening on this as happened on the below answer.
Also look at these.
OK, looks like the storm of emails has stopped for now.
I digged in to what was causing this to happen and think it could be an Outlook/Exchange issue - I actually asked a question on stackoverflow to see if my suspsicions are correct: http://stackoverflow.com/questions/21767712/does-outlook-web-access-pre-fetch-or-pre-load-links-from-html-emails
I also raised a bug report in ANSWERS to fix the problem in Answers that makes it vulnerable to this behaviour: https://jira.atlassian.com/browse/ANSWERS-1291
Thanks everyone for your patience, and for taking the time to report the issue to us - without you raising your hand we wouldn't have known this was happening.
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