or would you have to specifically think all your scars away?

Since we only saw Carl healing injuries once he noticed them (the wound on his head didn't heal until he looked at it in the mirror), I think you'd have to think them away.

If you suddenly developed the ability to heal and regenerate yourself with your mind, would your existing scar tissue immediately revert, or would you have to specifically think all your scars away?

Really, isn't scar tissue something new? You'd be thinking the keloid tissue away, and then re-growing the old skin the way it was. Which, if you can regenerate, and you're kind of vain, I guess you might do. But it seems like a hassle to do that for every scar you've got. I think I'd only ever do it for new things right in front of me, you know?

You'd be thinking the keloid tissue away

Keloids are a specific sort of scar tissue. I'd certainly start with keloids, because they're pretty ugly, but why not fix everything?

You don't consider OCD an actual physical limitation?

Was he OCD? I didn't see the beginning, just the parts around the explosion, the firing, and Jack telling his daughter that an unwelcome houseguest had mooched his way into their home.

I don't know if they named it, but he certainly seemed that way, for the TV version of a diagnosis.

I'd certainly start with keloids, because they're pretty ugly, but why not fix everything?

Well, but you start with the ugly, right? (I've got a humdinger up one side of my leg.) You'd have to know anatomy pretty well to fix the rest, or even know what needs fixing. If you're not careful, you could grow a whole new leg out of an old busted kneecap!

...this is why I will never write Sci Fi television, isn't it?

You'd have to know anatomy pretty well to fix the rest, or even know what needs fixing

He knew enough to fix a wound--replacing scar tissue with normal tissue seems to be of a complexity.

And who knows? You need to know a lot about mechanics to design a robot that walks, and absolutely none to walk yourself.

From the Chicago Tribune [link] :

What does a show do when it hits its 200th episode? If it’s “Stargate SG-1,” it makes fun of itself. A lot.

The “Stargate SG-1” episode titled “200,” which airs 8 p.m. Friday on Sci Fi, is one of the funniest TV outings of the summer, at least for this fan of the show. I can honestly say the episode, which is full of in-jokes and light-hearted fantasy sequences, made me laugh until I cried.

But you don’t need to be a longtime fan of the long-running program to enjoy its jibes at sci-fi clichés (beaming technology that works under highly suspect circumstances) or expedient writing (when in doubt, throw in some zombies). As one character says of the script for a proposed “Stargate SG-1”-inspired movie, “All these writers, and they couldn’t come up with something better?”

Spoilers follow, but I didn't read them.

I thought for sure that "10% of our brains" fallacy was completely played out.

As others have said, I was willing to let it slide with the "at one time" disclaimer.

My best guess is he's able to apply his entire brain to all tasks, rather than each part doing its own thing, though I have to think that could seriously screw things up, like senses going off-line because he's busy trying make himself fly or something.

“All these writers, and they couldn’t come up with something better?”

BWAH! 'Cause as we all know, the more writer names there are in the credits, the better the movie will be.