[hannob]

So "Go to superspammysite.com for horny pictures" is still an allowed username, right? Or of you skip spaces "superspammysite.com" may be enough that some spammer wants to abuse it.

I think you can't restrict usernames enough to not allow any spam. The only right way is to really just have the email and nothing else in the first confirmation mail.

[Semaphor]

Then you have "Hello superspammysite.com, welcome to our website." Not enough space for some kind of scam-text like in TFA. And considering that this has not happened in the last 27 years, it does not actually seem that worthwhile for spammers.