Why do VOID questions, which are only used to display text and do not record any data from respondents, create columns in the MySQL database with fields that are always set to "void?"

Yes this is odd but needed to make the JavaScript on the client work. In QPL, VOID questions are just questions that don't have data. The fixed-format export file and on-line tabulation report do not include void questions but the askSam and tab-delimited files do include them. In some cases you can just put your comments as part of a question that does collect data and avoid the overhead of an extra database column. But sometimes, there isn't an alternative to using the void question. If you were working with the MySQL file for your analysis, you could dump the data table to another location and then write an ALTER TABLE statement to drop the VOID columns.