I just realized what was wrong with what I was doing. I can't find out how to delete the issue but I now realize that it "Works As Intended" and makes sense.
I searched for map zooming bugs and this one seemed to be unique. I'm sorry in advance if it was already reported.
The weird thing is that it doesn't even change the light levels of blocks below it but makes everything look darker.
Footsteps are a new particle that show where you've been walking.
I've experienced this too in all F5 views as well.
I was just about to add this problem but I know exactly what you mean. This has happened twice in my world and it is problem that is just way too annoying.
I'm trying to use it in the snapshot to reset people to their spawnpoint in a map that I'm making. It's just easiest to do /kill to tp them back as opposed to teleporting them to a certain spot because it also resets their health.
I can definitely confirm the behavior where horses don't move until after they are pulled by a lead. Also, I can slightly confirm the behavior where they don't move at their regular speed until pulled by a lead. I remember having my fastest horse not running as fast in my survival world but I don't remember if just getting off the horse and then getting back on fixed it or if I pulled it with a lead.
Dang, That stinks that it won't stack now. I guess I'll just have to give my horses armor now to make room xD
Horse speed is random even if two horses are the same breed. Some are slow and some are fast. You are probably just getting the bad horses when you are spawning them in creative.
Torabi, I haven't checked how far the flow goes but what you seen in the picture is nearly every lava stream from the roof of the nether looked like. It took quite a while for lava to advance downward by just 1 block. This doesn't only happen with lava flowing strait down, but also for lava flowing sideways. The speed of the flow in the overworld is fine and unaltered. I don't know if this helped explain what I was saying.
This problem also affects version 1.10 slightly. I've found that if I have a LAN server open for an extended period of time (I haven't tried it with and without allowing cheats), the world will save but it won't go back to the main menu. I have to CTRL+ALT+DEL to end the program or wait until it pops up with the "Java Platform has stopped working" screen.