Andrew Castle was saying stuff about how you shouldn't let your opponent know you have lost your cool. The thing with Andy is that he's often muttering away or getting annoyed at himself for missing a point, so it's not as if his opponents can read a great deal into it they didn't already know. I'm also of the view that while it's a nice idea to keep your cool, if you are wound up, it's better out than in.
I'm not having a go at Andrew, except for the fact that when he and Tim are commentating together, they do talk a load of banal nonsense. Apart from anything else, he is entitled to that opinion, but in this instance it felt like an obligation to say something, and so he trotted out the received, if irrelevant, wisdom.
When someone like Federer starts griping and shouting at the crowd, you know he's properly riled.
I was following the match yesterday on Live Scores and keeping an eye on twitter, and going by twitter, the majority think it's funny when Andy swears at himself. There were a few po-faced comments, but they appeared to be from people who didn't want him to win anyway.