And DC forbids recap pages.
Animal Man sorta has one, but that didn't seem to do it for the readers. Which is a pity because I thought the book was quite self-contained, but if new readers say it's not then you should be listening to them, not me.
The "forbidding thought balloons" thing is pretty much an in-name-only thing; we still have thought balloons, they're just shaped like narration boxes now.
Absence of omniscient narration...well, I'm of two minds on this. I think too many old-timey comics use narration boxes to violate the fuck out of "show, don't tell"; look at an early Batman story sometime for an example of a comic where EVERY SINGLE PANEL has a narrative box describing the exact thing that Batman is shown doing right under it.
On the other hand, I've been reading some Savage Sword of Conan, and by Crom Roy Thomas is a master at the correct use of omniscient comic-book narration. His captions clarify things that aren't immediately obvious, grant a perspective other than the hero's, crank the tension the hell up in stories that would otherwise mostly consist of Conan walking around temples and scowling, and, yes, tell us who the fuck all these people are and why they matter. They hop the fuck around in the timeline (going, for example, from an adaptation of Howard's very first Conan story to a much later one where Conan's throne's been usurped -- skipping entirely over the part where he became a king in the first place) but even when you feel like you missed an issue somewhere you get all the information you need.
I think part of the problem is that they're still very much writing for the trade, deliberately leaving stuff dangling to explain later. (Batgirl seems to be the most egregious example of this; I haven't read it but both new fans and old seem infuriated by the huge emphasis on The Killing Joke and lack of explanation on how Barbara's up and walking around.) Obviously a little of that's okay. But I think more to the point, Stan didn't just give you "Yes, this is a mystery" notes, he also made sure every issue could be read on its own even if he was building an arc with it.
He also used footnotes, which are another of those things that are out of vogue with most modern editors -- I saw a lot of them in Men of War, mostly to explain military jargon, which is a great and appropriate use for them.
I do think it's telling that the readers had the fewest questions about Action and Detective, because they already know who the fuck Superman and Batman are. (NOTE TO DC AND WARNER: This means you can stop retelling their goddamn origin stories.)