First pin it by swiping it up, then swipe the notification.
I've also noticed that multi-touch works, i.e. one can hold the notification icon with one finger and interact with the notification with another. This includes swiping it away.
I've been using AcDisplay for a couple days now after having used DynamicNotifications for months. I'm really liking the UI of the beta. There is one feature I would like to request, which is adding an option to have the display turn off when all notifications are cleared remotely from within Android itself. Basically, the way it works now if I swipe away notifications from AcDisplay so that the unlock icon shows is fine, but if, for example, AcDisplay is showing only a notification for an email, and I check the notification from my computer causing the notification to be cleared on the device, which in turn causes the notification to be cleared from AcDisplay, if it was the last notification in AcDisplay then the screen should turn off. I hope this makes sense.
Also, here's a couple workarounds I found for some features that were missing:
The first feature is the ability to have AcDisplay always on when there are notifications showing. The way I got this to work is by modifying the values for timeout_normal and timeout_short in /data/data/com.achep.activedisplay/shared_prefs/config.xml
The second is having Tasker control when AcDisplay can come on. I use an NFC tag next to my bed to trigger a sleep mode in Tasker (I can't set specific hours because my schedule is too inconsistent) this does a plethora of things including turning off my bedroom lights. I wanted it to also be able to turn off AcDisplay. To do this, Secure Settings is needed. Simply configure Secure Settings to disable notification access to AcDisplay. Then, when my alarm goes off and triggers my wake up mode in Tasker I have Secure Settings enable notification access to AcDisplay.