ideally, your character saves are not deleted. the backups are for if your stuff does somehow get cleared out. (like if your web browser is set to clear out the flash cache)
i am planning to move the character voice stuff to the scene menu in next animtools, since it ties into character code.
if someone wants to dabble in actionscript, it would be possible to create a backup of charcodes in a cleaner text format. the .sdt files are a bunch of CustomCharacter objects. they only look like garbage because it has bitmap data:
public class CustomCharacter extends Object
{
public var ver:String = "1";
public var charName:String;
public var charData:String;
public var charShot:BitmapData;
public var haveCharShot:Boolean = false;
public var ID:uint;
public var dialogue:String = "";
public var menuPosition:uint = 0;
but then you would also have to make a way to load them, which would take more effort.
if you search a .sdt file for 'charName:' you should see the string of charcode text, though i never tried editing them. would probably be safe with notepad++ in hex edit mode.