Tyrone
As per the authoritative reply from Sami hafta say I'm firmly in the threading dial on the right camp. But I'm no pro either.
Way I see it the only time you need to look at a threading dial is when engaging the half nut so the tool will generally be clear of the work. Having the job out of direct eyeline is of little consequence. Half nut, or third shaft lever on machines like my Pratt & Witney, are almost invariable right of centre too do your attention is going to be that way.
Having it on the left puts it in the flying chip line of fire so its likely to be abraded over time. On gearbox equipped lathes a left side dial tends to be the travel limiter when going towards the headstock, maybe so much so that excessive tool or topside overhang is needed when working close up with a collet. Also tends to get in the way of a turret type bedstop. Which would seriously upset my working mode. My scrap bin find 6 position turret stop has been on at least 6 lathes so far. Not fitted any properly but all well enough to be indispensable. Never made up my mind whether the monster tube style multi-stop thingy sometimes seen hanging off the right hand side of the apron on old style Colchester Student, Masters and Triumph counts as a good idea or overthinking a work around 'cos the threading dial on the left gets in the way.
As a pragmatic Sussex country boy I'm permanently unconvinced by the Italian style argument. All too often style is an excuse for not spending enough time getting the basics right. I'll admit to really liking my Lancia HPE Auto but there were times when the idea of fricasseed Italian designer for dinner was, ahem, "tempting". Like having to pull off glued down trim to get at one of the relay and fuse boxes is good idea! And the less said about the braking system the better. Even if I did get it half price 'cos the brakes seized the day before I was going to buy it.
Clive.
PS Slow on the keys today!
