When I walk on a floating layer of snow (MUST be single) it wont count as transparent. If it's the Stacking snow feature then I'm familiar with it
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Confirmed in 13w24b.
Ok, it wont let you pass through it from the bottom either
Confirmed you cannot actually create this situation in vanilla.
Also not sure what the bug is? O.o
Although the easiest way to get this into vanilla is MCEdit (or something of the sort), it is possible to do it using only Minecraft, in conjunction with MC-6387.
The bug is that, in the past, the player would try to stand at the bottom of the layer of floating snow, and then immediately fall through because there was no block there. Because of the changes to carpets in 13w24a (including the fact that you can walk on floating ones), floating snow acts as a solid block.
I used MCEdit to obtain the floating snow, but I have encountered that snow layers merging into a pond sometimes spawn floating. Which can be a Vanilla way to test this bug
Still active as of 1.6.2, and 1.6.1
Still active as of 1.6.4, and 13w39b
still active as of 1.7.10, it is probably some thing that they thought didn't matter when they added thick snow

Still Works As Intended.
So then its a MCPE bug that you can walk through it

PC Edition and PE Edition don't need to be identical, there may be even more differences in the future.