It was stated in the blog at one point that levels from the Level Portal will be automatically rated on difficulty based on the amount of deaths before clearing a stage.
For clarification, this seems to imply that only runs where people complete the stage actually count (the same for rating the fun).
Are the ragequit counts going to come into consideration as well (or should they)? To avoid having quitting due to other means interfering with the stats, the "ragequits" could become weighted based on the amount of deaths made prior to quitting (so that starting a stage and then leaving to go to school or something doesn't change the rating at all).
If the death toll is updated regardless of stage completion or not, then this topic can be disregarded, but clarification from Edmund or Tommy would be helpful because that blog post was a big vague