[paperback]

One issue with regex is that it does not appear to be able to ignore diacriticals. IME, this is often necessary because diacritical marks may have been incorrectly applied and need to be replaced.

For example. suppose you want to find the word "protege" (i.e. protégé). It will not return any results if there are diacriticals in it, unless you enter the letters with the exact same diacriticals..

Calibre needs to have a setting allowing it to read letters with diacriticals as ordinary letters. This will allow the user to find all instances of the word even if the diacriticals have been incorrectly applied.