One that I don’t think has been mentioned. I hate those “I deny the existence of this work” posts. Something “I really loved The Matrix. Thank God they never made a sequel to it.”
I still think of those as the new in jokes. The old in jokes were about ketchup and tow trucks and wallpaper.
The 1980s called, they want their Olivetti back.
This is the Web, granddad. Underlines are for links. Bold or italics (or 18 pt green Comic Sans) for emphasis.
People who correct other people in a post. Hell, I just realized it’s not posting styles I hate, it’s the people posting.
It gets on my nerves because, in this part of the world, it means the topic’s already been debated and an outcome reached or decided upon. So, if it’s resolved, why is it in Great Debates?*
One of my annoyances are people dismissing other’s concerns with a snide declaration of “First World Problems”. Yes, I know there are starving kids in Outer Sandistan and in comparison to that, the lack of cellphone coverage at your mum’s place (for example) pales significantly, but it doesn’t change the fact that it’s still an issue for hypothetical you and the fact other people have it worse doesn’t automatically invalidate said problem.
*Yes, I know it has a different meaning in the US.
OPs that ask for info that never return to acknowledge the information, say thanks, continue the conversation etc. I’ve seen posters give detailed, informative or creative info and the OP never ones back. Arggggh.
Well, can you really blame them?
Yes, we can.
If a topic is important enough for you to start a thread on it, the least you can do is acknowledge the people who took the time to reply. If you make a habit of doing it, people will either quit posting in your threads or post just to bawl you out for never coming back to your own threads.
Uh, yeah. 
I think it has the same meaning in the United States. It’s just the form of the debate. The person proposing the proposition says “Such and such has been resolved,” inviting the debaters to agree or disagree with this resolution.
It’s OK if you put the exclamation point after it.
I hate it when the first sentence in an OP is “Thread title says it all” or a variation. This can be irritating in two ways. First, the poster usually doesn’t believe what he said, because that sentence is almost always followed by more sentences to say what the thread title did not. Second, in the rare cases where the sentence stands alone in the OP, the OP usually has to post multiple replies clarifying his intent after a couple of other posters misconstrue the intent of the OP.
I don’t hate this, but a number of titles end with the phrase “(long)”, leading me to expect an essay. But a number of these supposedly “long” OP’s are, imho, pretty short.
An example. The OP is only 440 words, which isn’t (to me, I guess) “long” at all.
I believe you… but it still feels a bit off to me. I wonder if the following phrases are grammatically correct:
*“Suggest me a new car”
“Demonstrate me how to juggle”
“Entertain me a story”*
Don’t we have prepositions for a reason? Aren’t they our friends any more? 
I hate when people put non-spoiler-ish shit in a spoiler box, repeatedly throughout a thread.
Don’t forget, puppy: Youth and skill is no match for age and treachery.
These sound weird. These do not:
How would you rather we say them? Give to me a beer? Give me a beer, please?
Give me two beers.
How 'bout “Gimme a beer, dammit!” :mad:
Or when people post spoiler warnings for things movies that came out years and years ago.
Hell, there’s a thread about the movie Signs in Cafe Society that warns about spoilers. Spoilers?! The film came out nine years ago!
I know the poster is just being cautious, and I’m not trying to give him/her a hard time, but come on. Nine years.