Cannot smelt wood other than logs into charcoal

Charcoal will result only when smelting items named "<tree name> wood", these are the raw items obtained from the trees. Processed/crafted items like planks or other wooden items will not yield charcoal (and currently cannot be smelted). More information: http://minecraft.gamepedia.com/Coal#Charcoal

You're right. The wiki says charcoal can be made by smelting "Any Wood", and I mistook that to mean any item made of wood, but in this case the capitalized "Wood" refers to the block named Wood, which is a log. This report should be closed as "Works as intended".