If a global search and replace capability is provided, the case of the replacement string should match the case of the old string, unless otherwise specified by the user.
Additional Information:
If a word is replacing the first word in a sentence, the first letter of the new word should be capitalized. If it is replacing a word that is entirely in lower case, then the new word should also be in lower case. However, the user should be able to replace a word with incorrect case with a correct version.