Sometimes an intern comes to me, and tells me how I should be writing code. I'm thinking should i take it out at the end during his performance reviews.

Depends, are they coming to you like "hey, it might be better if you do it like this" or like "hey, you should do it like this“¿
The first one is something I did to my (techy) boss dueing my internship. She appreciated it because she knows we learn from eachother.
The last one is bossy and you could tell the intern that its better to not demand it. If its a suggestion you could discuss it.