Questionnaire (plugin)

Is it possible to have a questionnaire that includes the respondent's user id or username, but not their fullname?

I notice the CSV of responses does include the user id, but only if it also has the fullname. I need to be able to match data from one questionnaire with data from another questionnaire, but I need it to be semi-anonymous (i.e. no personal info with the questionnaire data - but still "trackable" and with the ability to match submissions both between questionnaires and in pre/post testing using the same questionnaire).

Could I use the "fullname" setting and then just comment out some code somewhere?

Thanks,
Scott