Is there a way to lock doors? I tried /cprivate like it says in the wiki. When I left click on the door after /cprivate is says I am successful but then people go right through my door and steal my chickens.

your chickens are opening the door and leaving.....lol no, but they can despawn. have you seen people go through the door, have you closed the door, are ther other possible ways in like through the roof or over a wall?

I did /cprivate on a door then saw someone go right through it. I even tried the /cprivate again and it said the door was already protected

oh, ok then, if you actually saw some one use your protected door then i dont know... if they killed your chickens in a protected area then it could be considered griefing. what i would suggest is either wait for a mod to reply to this thread (they might not, who knows, they are pretty good bout that), or to make a pe in game at the door explaining the situation, if you cant add every thing when making the pe the there is a way to add additional info as a comment, instructions are in the wiki, i dont remember off the top of my head what they are