[Dovecot] changing fs separator for maildir (suggestions?)

Since we're migrating from an existing system that allows periods in folder names, I believe we must continue to allow them. So, I am deciding what to use as the separator instead. Right now, I'm leaning towards the backtick (`), since I don't think I have ever used it unless I was trying to execute an external command in some code. So, can anybody think of reasons not to use it, or have a better idea?