A somewhat similar problem happens when other fields, such as email address 
are invalid, see: http://psf.upfronthosting.co.za/roundup/meta/issue591
On bugs.python.org we have a detector to check them 
(https://hg.python.org/tracker/python-
dev/file/default/detectors/userauditor.py -- I don't know if Roundup does 
any attempt at validating the other fields), but this is only triggered 
when the user clicks on the confirmation link.
It would be good to have a way to trigger the detector as soon as the user 
submits, without having to wait for the confirmation email.