You gotta hand it to Delta. The Delta.com multi-city search function has been pretty useless if nonfunctional for years. Now, they've removed the ability to use pay with miles or attach e-credit certificates when clicking through to Delta.com from Book with Matrix and ITA Flight Matrix. For e-credits you now have to start a new booking search after selecting which credit to use in your Delta wallet. Before after you selected the credit it would take you back to your pending travel. No more. And while a phone agent can attach an e-credit to any of the valid routings or fares you find through ITA Matrix, you can only use pay with miles on Delta.com. Yet another example of Delta sticking it to us.