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.
With both Harry being a Slytherin and Ron not meeting him on the train, Ron is set up as a major antagonist to Harry and his friends. Ron looks down on Slytherin, just as he does in canon. He's not evil (yet?) but he is a more extreme version of the canon character.
Hagrid is portrayed as an alcoholic rather than someone who has a drink occasionally. The author uses the same incidents of his drinking as are present in the canon, but they are viewed negatively by Harry's friends and thus by Harry.
Too Cool to Live: In Y2, Hermione, previously relegated to obscurity in Hufflepuff, once again attempts to brew Polyjuice Potion to infiltrate Slytherin. She is killed by the basilisk. The author has stated that he didn't have a subplot to deal with her and wanted to honor her by demonstrating her work ethic and determination (widely regarded as defining traits of Hufflepuff).