The rules regarding healing up from Heavily Damaged/Wounded to Light Damaged are the same as before (you need to get equal to or under your Toughness Bonus in wounds lost to move back up to Light). The example of play to demonstrate this treats it different, however, specifying that the threshold for moving from Heavily to Lightly Damaged is the same as moving from Lightly to Heavily Damage (2xTB). Does the old rule from Dark Heresy stand, or has it been changed in Rogue Trader?

Interesting. I think that last sentence is incorrect. Since the rest of the rules (including the first line of the Heavily damaged rules and the example) agree that more than 2x TB is heavily damaged, I'd say that the last sentence referring to "equal to or less than TB, he becomes lightly damaged" is missing the "twice" before "his Toughness Bonus".