On macOS, please use the build-in “Archive Utility” to unzip the SOTorrent files downloaded from Zenodo, for example:

/System/Library/CoreServices/Applications/Archive\ Utility.app/Contents/MacOS/Archive\ Utility CommentUrl.csv.gz
mv CommentUrl CommentUrl.csv

The output of:

file -I CommentUrl.csv

should then be:

CommentUrl.csv: text/plain; charset=us-ascii

See also this issue description.