It's meant to be an invisible barrier; it doesn't make any sense for the fences/walls to connect to what appears to be air. I'm currently using barriers as a way to stop players from enderpearling through 1x1 gaps in a fence wall, but it's terrible aesthetically. Mojang definitely needs to see this.
Yes, I've tested and it is still the case that set damage values on weapons and armor are ignored in 1.5. I will update it now, thank you.
Intended. This is the "repeater locking" feature added in 1.4, which allows repeaters to save their state when powered from the side by another repeater. The bedrock texture indicates when the repeater is locked.
Custom spawners are, in fact, a feature of the game, and should be properly implemented now that their capabilities have been expanded in vanilla. This update has been almost entirely dedicated to giving map makers much broader tools to work with – it seems like this is quite an issue for anyone who wants to have randomized loot drops in their maps!
Sorry, I'm new to this and wasn't aware of the built-in attachment system. Now you don't have to go through an external website!
At least with lava, it doesn't have to be a slab. There can be a full block between you and the lava, and standing beneath it will make the screen orange as if your head is actually in a lava block, even though it is an air block.