These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Jerkass Woobie: Dear Celestia, Trixie had a hard life. Of course by the end of the story she loses/drops the Jerkass part.
Narm: Some of the more emotional points in the story will be interrupted by a simple spelling mistake, or the author will leave out a crucial word in the sentence. While not moment killing, it can get a little jarring at times.
Squick: The ultimate fate of Trixie's Mother. Her horn develops the unicorn equivalent of a necrotizing disease, causing her a quick but painful death.
Tear Jerker: Many. Most notably when Twilight thinks Trixie is dead, trixie finds out how her father died, and ends up crying herself to sleep and Twilight and Trixie seem to pull an I Want My Beloved To be Happy on each other.
Wangst: Twilight's pining for Trixie sure comes across as this sometimes, especially once she leaves. It's all an act, of course. Of course, when she realizes Trixie might be dead this is Subverted, and then Double Subverted when she reveals She's a Chessmaster who's been playing every angle of the wizard duel that drives the plot the whole time.
The Woobie: After growing out of her Jerkass traits, Trixie's left behind her arrogance and and made herself at home amongst Twilight's True Companions. She is still a very sad character. Losing your parents at a young age, and accidentally killing one of them (or at least thinking so), will do that to you. Twilight Sparkle counts too when she thinks Trixie is dead and when Trixie says she can't and doesn't love her. Subverted in that she knew Trixie was alive and in love with her the whole time, and was putting on a front to help her win Trixie's affections. See The Chessmaster entry on the main page for more details.