Nope. Only RAW. That could be a raise too much of shadow though.
Then: could it be some 'over-sharpening' in post-processing + JPEG compression you use when re-saving image for posting on forum?
I just tried to check my 6D images that may have areas prone to JPEG artifacts and halos and saw none...
Here is a sample of simple 'walk under the tree, point camera up and shoot' scene. It's out-of-camera JPEG, no extra processing at all. No halos (just unsharp corners of 17-40 at f/4).
Ooops! It looks like the forum engine efficiently re-compress the image and kills things "no one" needs (like ICC profiles). I think I'd bttere post is as a linked image: