The Xbox version of D2:ED had two options to invert the camera (both needed to be checked to invert the camera for dragon form). The Xbox version of DKS has a single option, which works in human and dragon form. I don't recall anyone reporting this problem with the PC version of DKS.
I tried inverting the Y axis in D2:DC and confirmed it works in human form, but not dragon.
EDIT to copy a post from below, so it is near the top of the topic:
Here is a download link for replacement D2:DC executable files with a
Y-axis 'hotfix'.
This is an unofficial update (no formal QA procedure, etc), specifically to fix the Y-axis invert problem in dragon form; if you don't want to invert the camera controls during flight, then you don't need this hotfix.
Rename the Divinity2.exe and Divinity2-debug.exe files in the install folder (add a .bak extension, or something) and copy the updated versions extracted from the hotfix zip file. I don't know if Steam will have a problem with the changed executables (it likely will if the cache is verified for the game), but the game can be started directly, rather than through the Steam client.
If there is a patch released for D2:DC at some point, then this fix will be officially included.
