It's dreadful isn't it @WandaVision2 It makes me cringe so hard, that I won't read the rest of the post.
One thing that MASSIVELY pisses me off, is when someone says ...
'I completely agree with you angrywhompingwillow,' ...
but doesn't quote what angrywhompingwillow has said, OR say what time they said it, so you have to go and scroll back through the thread to find out what that poster said!!! 
There are a myriad of annoying words and phrases that a few people use on here, and I judge massively anyone who says...
Are you thick?
Are you on glue?
Do you have comprehension problems?
Are you being deliberately obtuse? (Just a way of saying 'are you thick' and staying inside the MN 'personal attack' guidelines...)
Picky bits (AWFUL saying!)
DDog, DCat, DNephew, DNiece. For FUCKS SAKE!
Just say, dog, cat, niece, nephew. WTF is wrong with you?! 
NO is a complete sentence. (It's really NOT!)
And it annoys me when posters say LTB (leave the bastard) for often things that most men do (and some women!) Like it's just THAT EASY to pack up your life into a few suitcases, and fuck off into the sunset towards a shiny new life! 
Also, posters saying 'chill out' or 'calm down' or the ever condescending 'you sound angry...' to someone who is a bit annoyed about something, or a bit pissed off, REALLY fucks me off. It's SO patronising and misogynistic. . May as well say 'stop being so hysterical little wumman!'
Anyone telling me to calm down or CHILL will be duly ignored, like they deserve. 