Set a jack-o-lantern on a block, break block, put chest under block, attempt to open chest, chest will not open.

Set down a chest, set glowstone on the chest, the chest opens.

I am unable to use the jack-o-lantern as a "cheap" replacement for glowstone if I need a chest underneath it. This would be the case if the jack-o-lantern is no longer flagged "transparent".