Hini, we cannot all assume that people who play this free software game we call DF on the open internet are all of responsible/legal age and mature enough to handle the content. Im quite certain that despite the learning curve, there are actually quite a few 11 -15 year olds (more or less added onto that number for a range) who probably should have some sort of supervision depending on age given the heavy topics that occasionally prop up in df, this one included. Though a heavy handed parental 'shut it all down' rhetoric might not be the answer, we need to account for the variable of who plays the game in order to be ethically responsible for ourselves (not that we need to publish, 'clean' versions and 'dirty' versions via a medium like signup to the forums, requiring enforcement but also convolution of the community by dividing content and discussion up)
If we had a defined age rating already, we'd be already verging on the 16-18 rating based off the explicit (not really graphic mind) fantasy violence alone with at best a 14 years of age rating. Adding rape/explicit detailed sexual content that may/may not be consensual to that would bump it up to a exclusively adult/mature title and likely call for censored/bans on versions of the game, treating it like its on the retail market for example.