depth of colour

Ralf,

There is nothing new about 16 bits support in Elements, and that's a good thing since PSE has 16 bits support when it's needed.
You are shooting raw? All internal computation is performed both in 16-bits and in a wide color space (a flavor of Prophoto). Remember that if you shoot jpeg, you are necessarily in 8-bits.

When you have edited in ACR, check the menu to open the converted file, and you have the choice to open either in 16 or 8 bits in the pixel editor. If you choose 16-bits, nearly all useful global edits are available. You know, those who enable you to prevent posterization. That includes a number of filters.

You have to know that for editing of details (sharpening, dust removal) with the tool palette, only 8 bits is supported: 16 bits has no visible advantage for those edits.

Also, you can't work on layers in 16 bits. So you'll have to convert to 8 bits before your layer work. Indeed, some strong creative blend modes can lead to posterization, but for normal blend mode and compositing, 16-bits editing does not bring any advantage, only more weight for your layered files.

So, I have set my ACR to convert to 8 bits to 'Open' in the editor.

Also remember that your resulting edited file will be viewed or printed in 8-bit only devices even if you are an advanced amateur.