He spends a while turning that one over in his mind while he strides across the desert. (Moving his body makes everything come easier, his thoughts, his feelings, his whole being. He's not fully consciously noticing this, just a little relieved in the back of his mind not to be standing still anymore.)
There's definitely something to it, at first glance. There's something to all of it. The idea of mercy as an expression of power, as refusing to let someone control him—that speaks to the same parts of him that have so much trouble with mercy in the first place. And the idea of himself and his feelings and desires as being like magic, a wild power that can be turned to a purpose or let loose to rampage unchecked, that can be controlled with careful attention and skill or slip free and wreak havoc...
...well, that's just true. Startlingly, kind of upsettingly, unequivocally and directly true. In a sense, that's just literally what happened, when he made his grand mistake. He got out of his own control, gave in to... Siran-fray... and did a bunch of stupid shit culminating in doing the exact same thing with magic, trying to spin up a spell too big to hold—though he held it for surprisingly long, in the end—without even a clear idea of what exactly he wanted to accomplish by it, and it tore itself out of his hands the way magic always does when you get overambitious with it. He can clearly see the echo there, the similarity in structure between the spell going wild and soaking the continent in spellfray, and his own ego going wild and grabbing for power in a mad idiot rush without thought to the consequences. And... it is, he thinks, a helpful way to think about himself. Magic is the way that it is, and you have to learn to work with it, and he did learn to work with it, he's one of the most accomplished mages in the world (though 'accomplished mage' is kind of a backhanded compliment at best, carrying as it does the fundamental connotation of the kind of reckless idiocy that's necessary for anyone to try to become accomplished as a magic user). He's starting kind of from scratch on learning to work with himself, but... the parallels are helpful in figuring out how to work with himself. There are differences too, definitely, lots of them, but the basic approach of 'this is a powerful force you need to learn to handle on its own terms, and until you do it will keep wrecking stuff every time you mess with it' is... apt.
He's thinking about his sword, now. He used to have a sword that ate spellfray. He was really proud of it; it let him cast spells that would've been stupid to cast without. He only managed permanent translation in the first place because of the sword. Also, it was fundamentally a tool of destruction, getting more and more unwieldy and inclined to lash out at everything in reach the more spellfray he fed to it, until he discharged the excess by annihilating a few trees with it. He lost it when he walked into a cursed city and got torn apart.
There's no reason why an artifact to eat spellfray has to be an engine of destruction. It's just... easier, to build it that way. If you want to build something to eat spellfray and you want it to do anything other than mangle things, you have to put a lot of careful thought into what exactly it should do instead, and how to get it to do that and not something else, because spellfray is fundamentally about not doing what you expect. It seemed at the time, when he made that sword, that of course it would be ridiculous to try to make it anything other than a dangerous barely-controlled weapon. But... he'd like to stop being a dangerous barely-controlled weapon. And he thinks, if he makes himself another spellfray artifact, he'd like it to not be a dangerous barely-controlled weapon either. And—most of the details of designing such a thing are going to be totally inapplicable to designing himself—but, he thinks, there are still useful parallels in the underlying approach, again. Creating, healing, helping, mending, these things are much harder and more delicate than destroying. Most things you do, if you're not being careful, will destroy more than they create. But if you pay attention and put the work in, you can find ways to build up instead of tear down.
(As a side note he's sort of confused by the 'deserve' framing; it's not a concept-structure his mind naturally falls into. Like, he's heard of the idea, he just doesn't personally tend to think that way. But it doesn't interfere much with his understanding of Zash's point, it's just a quiet little aside as he considers things.)