In this HDR, when I turn up the dehazing in Lightroom, it produces adverse effects that wouldn't usually happen if I did the same adjustment to a regular raw image. If you look at the hill line, there is a strong dark edge bordered by a bright edge above it. I tried to minimize this, but it's still prevalent. Why does this happen and is there any way around it?
The short answer is the dark line/bright line border is already there in your HDR image, it's just not as noticeable. When you apply the "dehaze" tool in Lightroom it increases the contrast between the brightest and darkest parts of the image. It does this because haze in the air tends to decrease contrast. So the border between the dark hillside and the brighter sky is emphasized by the use of the dehazing tool. If you push it enough you'll also get "halos" around the windmill silhouettes.