However, I am putting together some teaching materials to show the deficiencies of editing in 8 bit mode... and I can't break the images. I took a few RAW files, processed them each into both 16 and 8 bit images and performed the same exact adjustments on each.
It can be safely assumed that any reasonable Raw converter (whether external or in-camera) will not drop high bit precision from the A/D converter until the main processing steps and final gamma encoding are accomplished:
/> 12 or 14 bpc from the A/D converter
/> high bit Raw processing
/> output set to
a.) 16 bit or
b.) 8 bit
Hence, with any small output space such as sRGB it will be hard to impossible to show that options a.) vs b.) are different "as they are" – unless further editing steps are added outside the Raw converter e.g. in Photoshop:
b1.) 8 bit left at 8 bit
b2.) 8 bit left at 8 bit for adding adjustment layers*, but changed to 16 bit before flattening the layers.
b3.) 8 bit changed to 16 bit
/> followed by further image editing (* with b2)
Now with Levels and Curves, etc. it will be hard but it’s possible to show that b3, b2 have a competitive edge compared to b1. However, very very drastic settings are needed.
But, big but, situation gets clearer once Noise Reduction plus some Re-sharpening are the first things to be done after b1 or b3. With option b3, this will fill the reservoir with 'real' 16 bit data which don’t have an integer 8 bit equivalent any more. Resulting files can tolerate further editing somewhat better before showing posterization. For example, take an image of a blue sky which fades towards overexposed white. Now, try some highlights recovery via the S/H tool. Under the provisions explained here, b3 will often enough outperform b1.
On this basis (!), the more challenging comparison might be between a.) an unbroken high bit pipe, and b3.) recovered high bit depth...
Hope this is of help.