It gets under my skin when a person posts about a problem with someone they're dating, then EVERYONE in the waking world tells them they're just not that into you, move on, etc. The OP decides to come back and say "wait I forgot to mention that, once in the year 1992 he said I was pretty." LOL. I'm paraphrasing just to be a jerk, but you get the idea. It's like, no, we can read, we can get the impression of your situation by reading your wall o' text, we get it. One thing is not going to change what we can plainly see and what you can't.
I also can't stand run-on sentences. I get that this is a forum and not an English class, and I also understand that phones autocorrect things. But how hard is it to throw in a period or comma once in a while? Or have mercy on our eyes by using the space bar between paragraphs?
On the flip side, sometimes when a person isn't a native English speaker, they apologize in advance for what they think might be a rough post, but it turns out to be well-written. Many times they write far better than others who've been speaking English all their lives and just choose to type in a way that no one can understand.
Sorry, I'm not normally a jerk, but I've been holding these in for a while.