I think that's a pat and easy answer, too. As I said:
These are the types of people who'd consider it downright blasphemous to talk about making comics more like another medium.
Good point. I guess I have to concede that one.
Still, I could use a little help. What are some other conventions that comics used for a long time but evolved away from? (And nobody mention Superman's trunks.) I imagine there's a lot less use these days of long, stilted expository dialogue passages, especially in the middle of jumps or kicks. Less use of characters redundantly explaining how their powers work or what the Bottle City of Kandor is every time it comes up. But those are changes in how dialogue itself is written, not so much in the stylistic presentation. Well, naturally, comics art has gotten more detailed, the colors more elaborate, although in recent years there seems to have been a trend back toward cleaner, more cartoony art styles, not just in young-skewing books like The Unbeatable Squirrel Girl and Ms. Marvel and Batman '66, but in stuff like Daredevil and Hawkeye as well. But what about more functional stylistic devices? Hmm, let's see, you don't often have comics panels pointing to the next panel, like they often did in the Golden Age. New techniques have been added, like on-panel captions identifying characters at their first appearance so that they don't have to be introduced through stilted dialogue (a technique also used in some movies, particularly in Japan -- Shin Godzilla used it constantly). So I guess there has been an ongoing evolution, and the shift away from thought balloons is part of that. It still seems a bit arbitrary to me, though.
One older convention I miss is the use of conversational narration and subtitles where the writers speak directly to the audience, especially the personalized way that Stan Lee did it. I think there was a fair amount of that in Silver/Bronze Age DC as well, though in a more impersonal way. It was goofy, yes, but it was fun. Although I think we are getting a bit of a resurgence of that in some of the recent stuff, like the hilarious page-bottom captions in Squirrel Girl, and the comical first-person monologues in books like Ms. Marvel and Hawkeye and Batgirl (of Burnside) help bring in that personal touch in a different way.