The wedding thread was from a woman who hadn't had the baby yet, and who was making plans for afterwards. In the opinion of many, she was being overly optimistic. Thus, many women were very concerned she would make concrete plans that she wouldn't be able to get out of, if things didn't go as well as she hoped.
On the other hand, Amanda Holden has had her baby, and presumably knows exactly how much or how little pain she's in, and whether it's costing her health to do this.
If Amanda had posted a thread (under a pseudonym!) concerning whether she should plan to return to work 2 weeks post-partum, people would've warned her it work out badly.
Mind you, I feel sorry for all the women who will be told "Amanda Holden was back at work after two weeks, and she nearly died . You didn't come near to dying. It's been 4 weeks. You're slacking"
Like other posters said, Ms Holden will have it easier than many other women, but dipsticks won't account for that when they're lambasting women.