"My 2 cents"
This has to be one of the most superfluous fixed expression in the history of the internet. Unless you regularly get asked to post other people's opinions under your own OSNews account, "my two cents" or "but that's just my opinion" serve absolutely zero purpose. They're just as annoying empty statements online as they are offline.
"I recently ditched Windows and..."
So, you switched away from Windows to another operating system - full time - and you're so proud of it that you have to squeeze into every possible story - no matter how unrelated the subject matter. Switching away from Windows doesn't make you special. It doesn't make you cool. It's certainly not information that has any effect on the world around you whatsoever.
Thousands of people switch away from Windows every day. It's like bragging about waking up in the morning.
"80% of users use only 20% of the functionality"
A standard quote, which is most often used when trying to defend OpenOffice.org. The statement is probably entirely correct, and I'm sure few people use more than 20% of the functionality of the more complex applications out there - the problem is just that for every user, it's a different 20%. Please, stop quoting the 80/20 rule to justify an application which lacks in functionality compared to its competition.
"I'm not a fanboy..."
Yes you are.
A lack of punctuation
Not using punctuation (which includes capital letters) does not, I repeat, it does not make you cool. It doesn't make you seem defiant, it doesn't make you different, it doesn't make you stand out. It only makes you look lazy and incapable. By not using punctuation you're advertising your own incompetence.
A lack of paragraphs
Related to not using punctuation, but maybe even more annoying. A lack of punctuation is technically bearable, but a lack of paragraphs makes your comment completely and utterly unreadable. A paragraph is a self-contained unit of discourse which covers a single point or idea. By not using paragraphs, you sound like a raving disorganised lunatic. Please lay off the coffee, and sit on your lawn and do nothing for a while.
A staccato comment presents an entirely different point in every sentence, making it impossible to follow what you're trying to say. Like a lack of punctuation and/or paragraphs, this is related to coherency. A comment which lacks coherency is a bad comment.
"What's the point of this operating system?"
Say you and your wife decide to have another baby. After a lot of hard work, she gets pregnant. After nine difficult months and the troubles of childbirth, you bring a new beautiful little person into this world. You could not be happier. This is the best moment of your life.
Then imagine me walking in, and saying: "What's the point in yet another human being?"
"I have a MAC."
I'm sure you do. If you're commenting on OSNews, you've got a MAC. In fact, I've got a whole boatload of MACs. I've got about as many MACs as I have network interface cards and network adapters. Please, for the love of the gods: the correct abbreviation of "Macintosh" is "Mac". "MAC" is an acronym which stands for Media Access Control (among a whole load of other things).
"Why is this on OSNews?"
Because I say so.
This is just a selection. I'm sure you boys and girls can come up with a load of other recurring comment annoyances.