Thanks for the feedback! 
One little thing that I think should be fixed, you should be able to back up
Something like that will probably be added in the future^^
And I would really like the be able to craft blankets for the horses that would work like the saddles to keep them still. My horses look kind of funny standing the barn in full tack
This sounds like a good idea, I'll put that on our list 
ok Red. I think this is the scenario. The player comes near via a TP movement
Thanks for the explanations! I think I finally found the issue that caused other horses to turn invisible or saddles not being visible etc, I guess the hotfix will be available in a few hours 
Here is another funny thing.. if you have two horse saddled and ready they soon begin to sync up and move exactly the same
Indeed... the idle animations need more variations... I'll put that on our list^^
Horses "whine" too much/too frequently, yet have neat sounds otherwise.
We will definitely update the sounds with the next update 
My major issue with horses is that they need some sort of "auto-run" similar to 'Skyrim' & 'Mound & Blade: Warband'
An "auto-run" feature is on our list, I think it's maybe about time to get it ready... maybe this will be added with the next regular update
You can't interact with objects when mounted, yet saw that it'll be changed later that I'm fine with this for "now"
Yes, at least it will be possible to use certain things like maps. In the long run, it will be most likely possible to use certain items like weapons as well, but that's a different story 
I can't keep my horse penned no matter what I do. It walks through walls, stone....
Unfortunately horses suffer from the same issues as other animals when it comes to collision detection, however, you can put a saddle on your horse, then it no longer moves 
2) I would love a black horse.
More variations are definitely planned!
3) I want to be able to craft hay stacks.
Originally we wanted to add hay with this update, but first we need a proper process to "craft" hay (i.e. drying grass). It's on our list^^
6) Please make saddles removable.
As @angriff mentioned, you can remove saddles by holding your interaction key (F) while looking at the saddle
If there are satchels attached to the saddle, you have to remove them first.
I wanted to ask you if you can insert the command to remove the poster
I'll put that on our list 
Ability for players to 'walk' their mountable animal via reins (so they can better place them in a stable)
Something similar is planned for all animals... unfortunately we have no ETA for that yet 
Ability to use map and weapons whilst riding (I saw you mention this will be worked)
That's indeed planned^^ Although being able to use weapons whilst riding is a specific thing that will be addressed in a future update (which mainly focuses on mounted combat)
Door hitboxes now wonky since update (I think you acknowledged this is a known issue)
This will be fixed shortly!
I love the dust trail Camel Donkey and Horse makes if you turn around after trotting. But only the rider can see this effect, players on ground do not see the kicked up dust, I presume this was done to minimize a performance hit on players?
It's a sync issue, I'll try to get it fixed for the next hotfix 
I noticed that the horse goes invisible at a certain point when you are far enough away from it
We reduced the render distance for all animals and npcs, this also affects horses... it mainly depends on your detail view distance. This reduces any "falling through ground" or "walking through wall" issues. Nevertheless, the animal AI (and collision detection) will be reworked in the near future, so we can maybe increase the render distance for animals again 