Another option:
on *:text:*hello*:#: {
if (%flood) { return }
set -u4 %flood On
msg $chan $chr(160) hi $nick
}
160 is a non-breaking space, and it doesn't get stripped away, so effectively there's one special space and one normal space, which results in double space.
You don't necessarily have to use the $chr identifier, you could just put those non-breaking spaces there manually: //clipboard $chr(160) and paste away!