import-mt sees comment authors as regular authors

Following the instructions (fairly simple) at http://carthik.net/wpdocs/importmt.html

I get to the step where it shows me the authors that will be created. I am expecting some, but the ones it finds make no sense, even lists a blank username. It seems to be picking up the Comment Authors, maybe?

The import.txt file is in iso-8859-1 because I have portuguese characters. I’ve set the Options:Reading Encoding to iso-8859-1, anything else I need to do to make this work? Is that the cause or…?

I have no gone on to the next step yet. Advice?

Thanks