[kh99]

You could try taking the space out of the pattern that condenses white space, like this:

// fix extra whitespace and invisible ascii stuff
$username = trim(preg_replace('#[\r\n\t]+#si', ' ', strip_blank_ascii($username, ' ')));

(the red is where I took out the space)

But I haven't tried it, and I don't know if that's all you would have to do.