[Dovecot] Force "lower case" Folder Creation?

We're exploring the use of "plus addressing" in our MTA (Exim), which
delivers "user+topic@domain.com" to a user's "topic" folder.

However, the case-sensitive nature of our ext3 filesystem means that
a message destined to "topic" won't deliver to a user's "Topic"
folder. For example, if a user creates a "Topic" folder, and gives
"user+Topic@domain.com" to a web form that lower-cases it, delivery
is deferred.

Although we're checking to see if Exim can workaround this, is there
a way Dovecot (1.0rc24) can force lowercase folder names without a
patch? We'd hate to do this but are exploring our options.

Thanks!

Rich