Yes omg. Yes. If the story provides no reason for a character to be acting OCC (and even then sometimes it's still a no) then you should not be writing them in that light. But haha English is my mother tongue and my best friend, who is latina has better grammar and spelling then me. I think growing up in NA, the school systems just let us be lazy whereas she learned all the grammar devices at an older age and could fully understand how to use them.

However, I also agree with you on that front too. You are writing, although fanfiction, have a bit more pride in your work. Simple errors such as 'they're, their and there' are very much unacceptable as is alot. Alot is not a word, a lot is. Alittle is not a word, therefore alot is not either.