When writing a reader insert fic DO NOT use I, Me, My and We, which is writing in the style of first person.
This type of language shouldn't be used in a reader insert fic. You can't argue with me on this. It's not the type of language suitable for a reader insert fic because it doesn't help to insert the reader into the work of fiction. It's hard to imagine yourself in the scenario when it's "I went to the 'mall' on a shopping spree."
When reading first person, the brain automatically thinks of it as a character doing that task or saying that sentence not oneself. As first person intends. First person is more I am telling the story, I am the character, you are a mere reader, reading about things from the characters perspective not yours. Therefore a reader can't imagine themselves in the fic. Although the writer intended for the reader to imagine themselves in the fic, hence it being reader insert, the fic because of the language used doesn't allow the reader to do so.
In simple terms the wrong language has been used so, for lack of better words I'll say, it's made the fic non inclusive. It's failed to pull the reader in and imagine themselves doing this or that with the person of pairing.
I, Me, My has about as much use in a reader insert fic as telling the a POC reader they're white in this imagine because the writer wrote "soft pale milky skin."
What language do I use instead?
You, Your, You are, Yours, and Yourself, which is writing in second person.
This is the best and only type of language a writer should be using in a reader insert fic. This is because second person comes across like you are being told the story but you are still the character in the story. Not that you're being told the story but have no place in it. Thus the reader is able to imagine themselves in the fic, doing this thing in the scenario and saying this or that.
In example "As you turned to look over your shoulder, you unintentionally made eye contact." or "You are stunned by the confession they had just made."
Just quickly when do I use first person?
In pieces of works that are *insert name* x OC. Which means the ship includes an original character so there is no room for the reader to insert themselves.
In short, a fic that is intended to have a character you've made up as the main character that's being shipped with person of choice. That is when you can start using I, Me, My, first person because the story is being told from the made up original characters perspective.
You can also use third person if you work is a original character x *insert person* fic. Third person is also an option in this case, however it is not in a reader insert fic for the same reasons why you can't use first person.
Just a note
Please take this tip into consideration, it's genuinely one of these that can help you to improve your writing and gain more responses to your works of fiction. If you don't want to that's *I say begrudgingly* fine because I can't make you. However please read this and understand what you are doing when you write a reader insert fic in first person.
Also I am British so I hate the word mall which is why its in '....' but I see even non American people use it in their fics. Its a weird word it doesn't make sense.