Oh, I didn't say it was strictly theatrical, just that this was his point of reference. As someone whose comics come from this place as well(my first series was adapted from a play of mine and I'm currently doing a version of Wedekind's LULU--and by the way, I was thrilled to see her show up in the new LOEG for this reason), I find his work technically useful to look at, even if, as a reader, it sometimes leaves me a little cold. Again, I think I may just not yet be old enough--I'm 40--to "get" his later work; I don't think it was being written with someone my age in mind.
But what I mean is that, rather than a "cinematic" approach which is composition-predominant, treating the figure as a subject in the frame, Eisner's approach is more "actorly," following the fluid ups and downs and dynamics of gesture. That he often foregoes any panel boundaries but very liquid washes that only darken, but don't bound, the edge of the storytelling unit, is one part of how this manifests with him. Think of how many pages you can think of in his later work that follow only the motion and speech of the figure, in a series of "peak moments."
That's only a very rough way of trying to describe what I mean, and while I myself try to let my characters "act," I'm more likely to edit those moments down than Eisner, because I try to have each page have its own beginning, middle, and end and rarely let a unit of action stretch more than one at a time. But I'm about plot. Eisner would give his stuff more space, because his stuff was, much more than the work of most cartoonists, focused on character, but not in a way of delineating the character's details, but more an ambient flow.
Again, clumsily put. Someone please tell me what I'm trying to effing say here. Argh!