dovecot - Apr 2007 - 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?