I have all sorts of pet peeves. Most of them to do with grammar.
Like, when people try to classify the word 'unique'. How do you even go about placing that word and its meaning into categories or states of definement? It's either unique or it's not. There's no middle ground or it would not be unique at all. You can have 'somewhat special' but 'somewhat unique'? At that moment, it is no longer unique or special.
There is also the case of 'Their'. 'There' and 'They're' type words. I understand it from a phonetic point of view, where you're sounding out how the word spells but otherwise, just maybe, these types of words are falling victim to a lack of understanding towards possessive words, omitted letters and so on.
The English language is a fine fettled thing.
I've had my writings criticised before purely because it was critiqued by an American reader. I am English and therefore I will use words like 'Colour', 'Armour' and so forth because that is how it is spelt and how it is pronounced.
Short postings... I can definitely agree on this and it's something that constantly crops up for me. There is nothing to bounce off from from a really short post. I have had to somehow derive a response to a single sentence before and that is incredibly frustrating. I come from an arts background in terms of education and bouncing ideas off of others is a fundamental process. No two minds are alike and thus bouncing off ideas helps to spark the creative process between peers. It's like answering a question, you'll use part of the question in your answer. I like quality but there's little quality to be found in single sentences that provide no use. I mean, sure, there are some single sentences that work but that's all about the situation to hand and the chemistry involced inbetween authors.