Yeah, my English is good, but it's still not my first language, so I can use the language oddly, for example misuse idioms and phrases or use a metaphora that works in Finnish, but not in English etc..
There are a lot of these things foreign writers writing in English can stumble upon.

If I were to write any more fanfiction than I have (I haven't written in ages), I doubt I'd write RPS. It seems difficult to pull it off very well.