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.
Fan-Preferred Couple: Judging by a poll the author took to gauge audience interest in early 2014, Harry/Ronnie is the favoured (possible) ship, with Harry/Ginny & Ronnie/Neville as each characters' second-most favoured pairings. The author has refused to comment on what couples (if any) will crop up once the characters become older and start noticing the possibilities, although he has noted that he would give indication if any pairings contradicting canonical sexualities end up happening - in this case Slash, since even Ronnie is strongly hinted to be straight.
The Untwist: Following Snape's resignation at the end of the first story, it's pretty damn obvious to the readers that Horace Slughorn will be his replacement. This is brilliantly subverted - the new Potions Master turns out to be Nicholas Flamel who, thanks to changed events, has elected to not die yet and continue assisting Dumbledore for a while longer.