Dragging an app's icon across in Dock without ended up pinning I like to keep the running apps in the Dock organized in a logical fashion, so that similar apps are grouped together. I don't pin all of them permanently because that would reduce dock icon size.

When I drag a running app to a place I want it to be, the app is auto-pinned. I have to right-click and unpin the app from Dock.

I wonder if anyone knows how to stop letting Dock auto-pin apps.
There is no setting for this; any item on the dock that you move gets pinned to the dock. Locking the Dock's content does prevent items from being pinned, but it also prevents items from being moved/rearranged.

You could download an alternative dock replacement that looks and acts like the OS X Dock (there are a few) and hide the real Dock, but that's about it. It may be possible to somehow watch the Dock for newly pinned items and unpin them every 60 seconds or something... but that's probably more hassle than it's worth. OS X doesn't always like to be tinkered-with like that.