Prose vs. Verse

Out of suspicion and curiosity, I compared my lines in our Arden with the Norton, and I was - only mildly - surprised to find that I was right: even these contemporary editions sometimes disagree on which lines are prose and which are verse. I'm definitely going to be attentive to this in the future and do what I did this time: if something doesn't smell right in the Arden, I'll look it up in the Norton. If it's just me, I'll see that and move on. If I'm right and it could be either one, then I'll know we've got a decision to make about that line.

I'm absolutely fascinated by characters' transitioning between prose and verse.

EDIT/UPDATE: Actually, I was wrong. I'm pretty sure the two parts I was looking at are set as verse in both the Norton and the Arden.

I was thrown off by the Arden's format due to the fact that Valentine finishes a line that Silvia starts; I think it's because of that that it puts "Valentine" and his words on the same line even though it's verse.

Silvia definitely catches him off-guard there, so I was surprised at first, but now I think it makes sense that it's verse, since it's short: it's short by a whole foot. So Valentine is not exactly at his most regular there anyway, but he still attempts to finish her line... and fails. Ahahaha...

Once again, these transitions fascinate me... though the matter is made difficult by quirks like prose that could scan perfectly as verse. For instance:

SPEED: Sir, your glove.
VALENTINE: Not mine - my gloves are on.

That's a headless line. But other than its headlessness, it's perfectly regular. The Arden even sets it as verse. But then - three lines later - it abruptly switches to prose. I get that Valentine was being poetic ("Sweet ornament that decks a thing divine"), but why was Speed, whose second line is set as verse as well?