When I installed Sierra I also profiled my display (with a spectrometer) and have been using the created icc profiles since then. Both Quick Look preview and the macOS preview app when displaying images will show weird colors though: cutout deep burned shadows! The strangest thing is that on the quicklook preview, the colors will be fine until I zoom in the image: After that it will darken, and never recover (until I reopen the preview).
This behavior happens for images (tested jpg,png and raw) that have an embedded profile, a referenced profile or are not color managed at all. Even with the Screenshots that one can grab with Cmd+Shift+3.
Photoshop and Affinity Photo display colors properly (and rather consistently) on all the above scenarios.
I discovered that it won't happen when the original display profile (named imac) is used, but will happen with all the other profiles, created both by basICColor and ArgyllCMS.
From left to right, the rendering of the same file in Preview(quick look is the same), Apple Photos App, Photoshop and Affinity Photo
Anobody having a clue what is going on? It's been bothering me for months!
Edit (an interesting discovery): I discovered that unchecking "embed color profile" while viewing the Export As.. dialog on Photoshop, exhibits a similar darkening issue that is fixed if I revert my System Preferences to using the default display profile. The file saved is fine though. Probably Adobe is using macOS's previewing capabilities inside their Export As... dialog? I wouldn't know.... Apple Photos app is exhibiting a similar behavior, but the results is not so exaggerated as it is in the preview/quick look tool
Here (on the left) is how QuickLook shows an image when I first open it, and then (on the right) when I double tap (with my magic mouse) to cause it to zoom. When the image is already 1:1 scale like this one, it won't zoom further, but the color weirdness does kick in anyways. Zooming out, doesn't solve the problem. One has to close QuickLook to recover original colors.