Minecraft wiki entry for Development_versions, associated text: Certain game mechanics, mainly a handful of different particles, have been modified to use 64-bit (double-precision) precision where they previously used 32-bit (single-precision).
As a result, the effects appear in the correct places even if the player is far away from the spawn point (with effects being the most extreme when over 16,777,216 blocks away).
The following precision loss errors are fixed:
Lava embers and popping sounds should now originate from the correct positions.[45]
Campfire embers should now be generated at the correct position.[46]
Particles from rain hitting the top of blocks should now appear at the correct position.[47]
Smoke emitted by lava during rain should appear at the correct position.[48]
Smoke emitted by campfires during rain should appear at the correct position.[49]
Particles from redstone dust should now appear at the correct position.[50]
Particles from redstone repeaters should now appear at the correct position.[51]
Particles from nether biomes should now appear at the correct position.[52]
Particles from adding eye of enders to end portal frames should now appear at the correct position.[53]
Particles dripping from leaves during rain will no longer snap to block corners and are correctly randomized across the underside of the block.[54]
The book of the enchanting table now opens properly at high distances; previously there were cases where the player could be pressed right up to the block, yet the book would not acknowledge them.[55]
TNT ignited by other explosions now appears at the right locations at high distances.[56]
Detector rails at high distances were not always being correctly powered and depowered, which has been fixed.[57]
Mob pathfinding caused mobs to randomly swivel at high distances.[58]
Mob spawning would also break down, spawning mobs at block corners and sometimes inside of other blocks.[59]
Generation of minecart with chests in mineshafts will now spawn them at the intended positions.[60]