Exactly what the topic subject says: how can I disable the autosave feature, in both FC and SC? It seems that the feature was included in the latests patch, and I don't like it, honestly.

It was always there. If you believe it is new then you simply never noticed it before. If you don't like it, ignore the autosaves. You can still save normal.

Really? Wow... I completed the whole game without noticing it :S

It's always been there. Basically, whenever you enter a new screen, the game makes an auto-save and you can retrieve the last 10 or so screens by opening the load window and navigating left until you reach page 0. It's not in place of manual saving, you can (and should) still do that. It's merely a welcome extra if you mess up or your game crashes. I can't see why you'd have a problem with it.

Note that while autosaving has been in there from the beginning, the text "auto-saving" in one corner of the screen is a recent addition. Before, it still auto-saved, it just did so without notifying you.