All translations from Levett and Burnyeat’s Theaetetus.
 
 A schematic of how I see readers and interlocutors.
The interlocutor ... You (on first read) ... You (the experienced Platonic reader) ...
... consists of only words on a page. ...are/have a mind. ... are/have a mind crammed full of all that is in the other dialogues.
... is constructed into a fictive person, with a mind, by you.
... are a witness and the mind that constructs the interlocutor.
... are an expert witness and a constructor of interlocutors, busy observing meta-patterns, seeing connections to other dialogues.
... exists in a linear fictional stream and experiences the dialogue inherently
diachronically.
... are reading linearly, but free to scroll around: your thoughts may be mostly diachronic at this point.
... know the full linear flow of the dialogue backwards and forwards, but are also fully synchronically equipped with all of Plato readily available.
... is mostly spoken of as a person in scholarship.
...are mostly ignored in scholarship.
... are the assumed consumer of scholarship.

Two  figures stand out in terms of taking interlocutors seriously and working on things relevant to what I am presenting here:
John Beversluis, Cross-Examining Socrates: A Defense of the Interlocutors in Plato's Early Dialogues, CUP, 2000.
Ruby Blondell, The Play of Character in Plato's Dialogues, CUP, 2002.