1. Flags on fences/walls
Flags seem to always follow the fences. This is mostly because anywhere else and they're too much in the way. Although I don't think they should ONLY be on fences it is frustrating to be tempted by that one extra square it seems like we're missing. This could be the advantage of building on a fence, aside from it being out of the way. As far as scents go I don't know. If you attack a flagged fence it should leave a scent right? If the flag is then destroyed I don't know but I would expect the scent to stay. I believe this would be more aesthetically pleasing then a row of flags all partially obscured by a fence.
2. Minimap authority overlay - most serious suggestion of the three
Its difficult to see where the radius' meet up (especially with statues) and where there will have to be another flag to cover a few measly squares. It would be really awesome if we had some overview of the authority that is currently in place. Like perhaps on the minimap. Please!

3. Prebuilt authority radius
It seems best to just build a straight line of flags (assuming no access to statues immediately) and build off of that in branches. However, this system makes it easy to overlap in places that are completely unnecessary. Especially if the walls are covered first and then the center is filled. If possible, it would be really nice to have a way to lay down potential flags that show their radius. This could be as simple as the building posts of flags/statues showing the red circles before they are completed. The problem is building in those would have to be allowed, just not allowed to be completed. Or it could be a separate buildable that takes one branch to mark a spot with the red rings around it. Placing the building signs ahead of time would allow the lawspeaker or chieftain to lay them down and have them built when they're not around. As it is now it seems like a lot of time consuming micromanagement. I want to say, "Go forth, my minions! Make my land blue and...authoritied!"