1) Neck & arm facings. I hate hate hate them, I always leave them out, turning the edge under or lining the top instead (I hate raw zig-zagged neck holes too, they remind me of school play costumes made out of shiny polyester by someone's mum)
2) The insistence on marking things using tailor's tacks. My school textiles teacher was obsessed by the things (that and linen), no tailor's chalk was allowed anywhere near the holy fabric. For the kind of polycottons I tend to sew with it really makes no difference whatsoever, it's not like I'm marking it with permanent marker.
3) The way patterns from the 60s for mini dresses always have the hem about 8 inches longer than your knees, just in case on of their customers from the Outer Hebrides or somewhere was put off by the skirt being daringly short on these new fashions (no offence intended to the fine people of the Outer Hebrides in the early 60s of course)
4) Pressed darts. I always slash the centre line myself and mark the widest part of the dart.