What happens if my co-poster suddenly disappears? Can I just write for his/her persona till s/he comes back?
Only if you have their permission to do so! When you begin a co-posting relationship with someone where there’ll be a commitment of time and/or storyline, you have the option to “log permission” with Council so your co-poster can take over writing for your personas in that co-post if you are unable to write for some time. The limits (such as how long this permission would be in effect, etc.) of that permission would be your responsibility to state. Also, it’s your responsibility to ask your co-posters to log their permission, too. So… if the unfortunate happens and your co-posters vanish… don’t ask Council to take away their intellectual rights to their persona just because the preventative steps weren’t in place.