In MS Word, it is rather a side effect than a proper feature. As for me, it is strange when a word processor replaces X with Y when you ask it to replace X with X.
Atlantis Word Processor has the "AutoCorrect After-You-Type" tool. Choose the "Tools | AutoCorrect..." menu command of Atlantis. It scans the active document for text fragments that might need to be corrected (including "straight quotes to smart quotes" corrections). Each reported correction can be accepted or rejected. The "Tools | AutoCorrect..." command of Atlantis suggests corrections according to the settings specified in the "Tools | AutoCorrect Options..." dialog. For example, you can instruct Atlantis to replace straight quotes with French or German quotes.