Backing out from isearch-case-fold-search

Let's take a one-question bug-or-feature quiz: In isearch, when you type in a capital letter, isearch becomes case-sensitive. However, when you delete the letter, the search *remains* case-sensitive. In fact, there is no way to make it case-insensitive without exiting and reentering the search. Bug or feature? I think it's a bug, and I intend to fix it. However, sufficient number of people claiming it's a feature will convince me otherwise (not to mention a veto of a member of the review board.) FSF Emacs behaves the way I want to make XEmacs behave.