Torches cannot be placed on half slabs placed on the upper half of a block. On the PC version, it is possible to place torches on upside down slabs.
Steps to Reproduce:
1. Either in Creative or Survival mode, place a half slab on the top half of a block.
2. Attempt to place a torch on the upside down slab and notice it is not possible.
I know I hate this but if you have mc edit you can place it on a regular block go into mc edit and delete that's block then place top slab it's will work but that is hard to do