We've launched the ability to limit a discount code to a first-time registrant only. 

When you look at your attendee list, you'll see a small label for "1st Timer". We display this as a way of highlighting people who may need special attention or welcome. It's available in the reports and can now be used to limit discount codes. Thanks to Patrick at SpeedSF for the suggestion!

We also fixed a sorting bug on the admin attendee list when the last updated column contained both timestamps "1/15/17 10:58" and relative times "20 minutes".