I hate people stating their opinions in one chunk! It makes it harder to read; thus most people, me included, won't read it. Your point will be void and the only thing others will remember you by is your sense of exceptional nerdrage and a lack of writing skills. I hate when they use bold, italic or underlined to show the emphasis of their flawed opinions about X or Y when it's been said and mould over and over again by other people thousands of times. Some people use an excessive amounts of exlamation or question marks, and yes, I definitely hate that too. One is enough, two if you haven't had your coffee yet and three/unlimited if the world has 2 seconds left in existence. Since option number 3 rarely happens it's ridiculous that so many people still use that in their posts with their flawed opinions.
That's all.