While talking about Dionysius Thrax you might add that the term obelisk as an editorial mark (used to denote parts of the text that were deemed to be added later) is mentioned in the scholia of this work, while discussing the legend of Peisistratus.
OK, I can't resist, I'll paste an excerpt myself:
"At some time the poiemata of Homer were destroyed, either by fire or by earthquake [...] But Peisistratus, the strategos of Athens, wishing to acquire for himself a reputation and to revive the works of Homer, devised this course of action. He announced throughout the whole of Greece that anyone in possession of Homeric lines should bring them to him for a fixed premium per single line. [...] and after gathering together all the lines, they summoned 72 experts (grammatikoi) to assemble the works of Homer, each one in private, in whatever manner he might consider the assemblage would be best. He [Peisistratus] summoned them for a premium that was fitting for intellectual men and kritai poiemata, and to each was given all the lines in isolation, as many as had been gathered together."
This, AFAIK, is the first mention of editors/scholars performing style analysis for authorship determination.