I do not believe there really is starting ceiling for when people can be "allowed" to roleplay; it is something inherent, going deeper than just a plastered on qualifying age that you find in many other places in life. In effect, everyone roleplays when they're younger to some extent, some just keep going with it as they age like the vast majority here. It tends to mature and adapt as they do, being a mirror-like reflection of who they are and where they are in their life. Not always exact of course, but if you cataloged every post and every character one created from the moment they started to when, or if, they gave the hobby up, things would alter noticeably; even if it were but language and word choice.

That said, there's no limit to starting roleplaying.

For more mature topics - mind you I am speaking predominantly about violence, gore, language and the like - it again varies. Some handle and grasp that reality of life and wish to reflect it from an early age, others push it aside because they would rather not dwell on the less pleasant elements in their life. Regardless, the choice is the individual's; I would gladly take a younger, more mentally mature roleplayer who can handle "tough" or "realistic" scenarios with their writing than an older, less mature roleplayer who cannot begin to even toy with the idea - of course that is assuming this fantastic scenario was were one encountered regular violence or cursing.

What is [i]not[/i] permitted - at least in my eyes - is an under aged player in a truly adult roleplay wherein he or she is exposed to sexual content. That has all kinds of legal ramifications that quite simply spell out doom for anyone advertently or inadvertently involved. Barring the law aspect it can lead to... less than noble types' involvement, should they discover it.

Only opinion.