A Thought Train Gone Wrong

I casually looked around the internet, and found that people use italics a fair bit. I thought to myself (note that it wasn't as articulate)..."Is this actually the correct usage for italics?". So I asked Wikipedia, a friend I've known for a while.

• Emphasis: "Smith wasn't the only guilty party, it's true".
• The titles of works that stand by themselves, such as books or newspapers: "He wrote his thesis on The Scarlet Letter". Works that appear within larger works, such as short stories, poems, or newspaper articles, are not italicized, but merely set off in quotation marks.
• The names of ships: "The Queen Mary sailed last night."
• Foreign words, including the Latin binomial nomenclature in the taxonomy of living organisms: "A splendid coq au vin was served"; "Homo sapiens".
• Using a word as an example of a word rather than for its semantic content (see use-mention distinction): "The word the is an article".
  • Using a letter or number mentioned as itself:
    • John was annoyed; they had forgotten the h in his name once again.
    • When she saw her name beside the 1 on the rankings, she finally had proof that she was the best.
• Introducing or defining terms, especially technical terms or those used in an unusual or different way:^[3] "Freudian psychology is based on the ego, the super-ego, and the id."; "An evennumber is one that is a multiple of 2."
• Sometimes in novels to indicate a character's thought process: "This can't be happening, thought Mary."
• Algebraic symbols (constants and variables) are conventionally typeset in italics.
• Symbols for physical quantities and mathematical constants: "The speed of light, c, is approximately equal to 3.00×10⁸ m/s."^[4]

I reckon that hardly anyone on the internet uses italics correctly, including me. Maybe not you. Because you know what you're doing. Then again, nobody knows.