There's a lot that's doubled in this play of doubles, so I thought I'd share a few tidbits I noted to push things in another direction...
I'm also still digesting Gilbert's comments and thought I'd offer a little close reading of my own in the meantime:
In Act II, scene ii, when Antipholus of Syracuse and Dromio of Syracuse were going back and forth -- the following lines resonated a bit more than usual.
Dromio: "There's no time for a man to recover his hair that grows bald by nature."
Antipholus: "May he not do it by fine and recovery?"
I'm not certain, but I think old Sylan Barnet informed me once upon a time, that in Elizabethan pronounciation heir and hair were puns (much like art and heart, the H's dropping away). This then gives another nuance to a man (Egeon) attempting to recover his heir (that was stolen away by nature), a man we encountered at the beginning of the play in need of a fine for his own recovery.
I suppose with the right delivery this unwitting truth could have landed quite nicely, adding another layer to the dramatic irony: they don't know the truth even when they're speaking it -- yet nonetheless, it's there, in the language, implying that for all the chaos in the play, this world is still essentially an orderly one, the Antipholi get to beat their Dromi, the hierarchy is still intact (as opposed to the fluidity of The Tempest, for instance).
I also loved the passage, later in the same scene, when Adriana says:
Do not tear thyself away from me!
For know, my love, as easy mayst thou fall
A drop of water in the breaking gulf,
And take unmingled thence that drop again,
Without addition or diminishing,
As take from me thyself and not me too.
What an image! And think how it resonates when uttered to the wrong Antipholus. In marriage, two people become one; with twins, one person becomes two. And we get to feel both dynamics going on simultaneously. The juxtaposition is heightened when this speech is placed next to the closing lines of the play: "We came into the world like brother and brother; and now let's go hand in hand, not one before another." It takes two to tango, but also to achieve equilibrium.
That's it for now, I'm afraid. Think of it as a tasting menu.