If he's talking about Xenophilia, then he's an idiot. I can honestly say it's one of the best fanfics I've read. The characters are very in-tune with those of the show, the romance is actually very believable, and it's main focus is surprisingly to develop Equestria society and inter-personal relationships between families and other species of that world.
Wow Dashie... Look at you proud stance and teasing face. I'm going to find away to get to you. No matter the cost. Rest assured as you stand there and am here I will never stop. Never until I hold you in my embrace. I dream of the day I see you again soaring through the sky with me trailing behind just enjoying the warmth of your smile. I will Always and forever love my Loyal, most Awesome, most Beautiful mare in the existence of Equestria. Im so close to you Dashie. With all my love in my heart, Midnight Flare
Just finished reading the last chapter of Xenophilia, and just to say it that was a beautiful story. Multiple times during the story a can imagine Dash standing and staring at Lero like this. Story address: [link]
That's the dock, or what some refer to it as the 'tail stub' (root of the tail). I notice that some artist get really technical with the anatomy and include it. It's actually a nice touch to add towards the characters. Weird at first, but its legit.