imo trying to make characters not be "mary sues" stifled me creatively for several years. the only thing that should matter is if youre going to be rping with other ppl with "mary sue" characters, and thats really the only time you should limit yourself but only in the way of not godmodding, metagaming, and/or powerplaying and similar. making "mary sue" characters is a lot of fun and the term "mary sue" is stupid and limiting! even the creator of the infamous universal mary sue litmus test, which i followed religiously as a kid, disowned the test and term.