The main characters are physically mature as far as I can tell. They're the same size as other adults, hold down jobs, and have romantic interests- at least in Rarity's case (but then so does Spike and he's considered a baby, so whatever).
Also
>implying that fans aren't already making as much pony porn as they can
I've learned to tolerate drama...except on the boat
I don't think PlutoniumFist thinks there's a lot of it already. I don't think most people would understand how you could find characters that look like this attractive enough to sexualize.
Comments
☭ B̤̺͍̰͕̺̠̕u҉̖͙̝̮͕̲ͅm̟̼̦̠̹̙p͡s̹͖ ̻T́h̗̫͈̙̩r̮e̴̩̺̖̠̭̜ͅa̛̪̟͍̣͎͖̺d͉̦͠s͕̞͚̲͍ ̲̬̹̤Y̻̤̱o̭͠u̥͉̥̜͡ ̴̥̪D̳̲̳̤o̴͙̘͓̤̟̗͇n̰̗̞̼̳͙͖͢'҉͖t̳͓̣͍̗̰ ͉W̝̳͓̼͜a̗͉̳͖̘̮n͕ͅt͚̟͚ ̸̺T̜̖̖̺͎̱ͅo̭̪̰̼̥̜ ̼͍̟̝R̝̹̮̭ͅͅe̡̗͇a͍̘̤͉͘d̼̜ ⚢
Nothing but pony porn would ever be produced by anyone, ever again! :P