Your essay seems to raise the question of for whom it is that an editor actually edits, and suggests to me that the postmodern edition is most valuable for those interested in performance. Marcus herself talks about editing Shakespeare to make it compelling to both "readers and performers," those for whom, for example, identifying stage directions or speakers is of utmost practical importance. But the need for singular knowing is less pressing on (for lack of a better term) "general" readers, who are not necessarily invested in translating the written document into another artistic medium. What does it matter to the general reader which of Titus's two sons would be speaking at any given time? The work doesn't seem to require a distinction, and indeed so seems to deliberately blur the filial and paternal relationships between the characters that locating difference would be undermining the point. Thinking further, the ambiguity that I surmise might be interesting for general readers could also benefit performers, who may be sufficiently inspired by textual variants to construct viable heretofore unknown stagings.

Editors' traditional obsessions with entrances and exits, or with stage directions, seem to be an attempt to limit theatrical possibilities in the hopes of providing clarity for general readers who might otherwise become confused; is it possible that editors' undisclosed assumptions about readers’ capabilities might be the real editorial problem? Does the notion that editions for performance require a different level of ambiguity from general reading editions hold up to scrutiny? And who put General Reader in charge of what editors do, anyway? (Also, on Titus, you may be interested to read Ian Lancashire’s paper in EMLS, which discusses the Q spelling of “Aron” in light of his Lexicons of Early Modern English.)