These are notes that apply to everyone though not necessarily everyone did these things:

1. Never say “I think” or “I believe” in argumentative writing. It’s obvious you think that, else you wouldn’t say it. Saying “I think” is a way of soft-pedaling your argument, providing yourself an out if someone disagrees. “I think” is followed by the implicit “but I could be wrong.”
2. Avoid “you” in formal writing. Period. If you can’t think of a way to reword it, say “one.” In other words, instead of “you would think” write “one would think.” (That’s a terrible example, though: you could write “it appears” instead of both of them.)