I thought if someone would be out a simple post was good enough, to be deleted at their return. Though maybe an "afk place" could be useful to avoid clogging the threads with messages. I don't know.
About asking for others to "play" your character if you're away, that depends on one's preferences. If you trust someone enough, good. Otherwise, if you know one can't answer for a period beforehand, just avoiding talking to that character should be enough.
A time limit could be an idea, but it shouldn't be necessary. Posting once a week shouldn't be a problem, otherwise see above. I'd say if someone doesn't answer for a week it could be assumed he/she has nothing to say for that round, but it may or may not work... Let's see.
About asking for others to "play" your character if you're away, that depends on one's preferences. If you trust someone enough, good. Otherwise, if you know one can't answer for a period beforehand, just avoiding talking to that character should be enough.
A time limit could be an idea, but it shouldn't be necessary. Posting once a week shouldn't be a problem, otherwise see above. I'd say if someone doesn't answer for a week it could be assumed he/she has nothing to say for that round, but it may or may not work... Let's see.