There are two third rails in MLP fandom which are very seldom mentioned or touched:
1) Realistic treatment of equine anatomy as influencing pony life.
2) The first generation (G1) continuity, with Megan and all of that. (Friendship Is Magic is technically G4.)
D.G.D. Davidson (whom we know as scificatholic) bravely goes forth to touch both rails at once in a fun new story, “A Mighty Demon-Slayer Grooms Some Ponies.” It’s got a lot of good stuff in it, so check it out.
Some horses really don’t like you touching their feet/hooves, but they have to get used to it or the physical problems described in the story will ensue. However, the depths of nerves that Rainbow Dash displays in this story (and in the original ep where hooficures were mentioned) suggests that something bad happened to her at some point. (Which may also explain why she makes a point of living off the ground, but alone; and it may even power her need for speed.) Horses admittedly are really good at getting themselves traumatized by scary things (like paper blowing in the wind) as well as by actual trauma, so it doesn’t necessarily mean that it was something Bad. But it’s a point that most fanfic writers seem to neglect, whereas most horsey fans seem to be very concerned about it as an important psychological point.
There’s also some fun links in the story comments to some of the old G1 comics and storybooks, which point out some plot points that show up again in MLP:FIM.