Within a day, I got an email back. He said sure, but asked why his comic wasn't in the "Comics of Note" list. I looked; and much to my chagrin, I'd accidentally mucked up the HTML so the link to his comic didn't appear. I fixed it, and sent him a reply explaining the error and promising to let him know when the episode posted. I was pleased that he responded, but it didn't feel very good to have him be the one to call me on the mistake.
So Wednesday comes, and I upload the episode with Abe and Preston in it. And open up the email he sent, so I can hit "reply," and it occurs to me that there was some ambiguity to our exchange. I had taken his response to be "sure, you can do it," but it could also have been "sure, I'll look and let you know." With the less-than-stellar dynamic of the previous interaction, I worried that he DIDN'T want me to use his characters, and bringing the episode to his attention was going to open the proverbial can of worms.
I admit that I briefly considered not sending anything, but that's not the Cowboy Way. So I went with flat-out honesty. I said that I realized his meaning could be interpreted two ways, I took it to mean that I had his permission, and I included a link so he could see the comic in question. I sent it off, and wondered if I would get a gruntled or disgrunted reply.
So far, I've gotten the second-best possible outcome: No response. In thinking about it, he must have looked at my comic already, or he wouldn't have known his link wasn't visible on the page. So it's possible I got all wound up for nothing. Odds are he's got so much else going on, this whole exchange was no big deal (to him, anyway). If I ever meet him in person, I'll ask.