Converting from 32 bit to either 16bit or 8 bit using HDR toning set to Exposure (0) and Gamma (1)
The preview is exactly as per the 32 bit file, and shows no difference checked or unchecked. Fine.
Then when OK is clicked, the image subtly changes.
See the flare area around light on this layered file.
Layer 1 is a screenshot of the original 32 bit image.
Layer 2 is a screenshot of the 8 bit preview in HDR toning.
Layer 3 is the 8 bit output, which is different to the two above.
May I know which version of Photoshop are you using and are you able to replicate this issue on a different file?
Also, Post your Help>>System info report here so that we can check the same.
There's been a few updates to Photoshop since I posted and running a test again it seems to be ok now. I'll run some more tests and see if the issue crops up again.
Thanks for the update. Let us know if you have more queries.