In reply to Timmd: Thanks for the reassurance. I swapped out the link wire at the weekend and the extra adjustability of the straddle cable means that I've been able to tune the feel of my rear cantis
much better.
The only reason I can find for the link wire ever being invented is that it eliminates the risk of the straddle cable cable dropping on the tyre and suddenly locking up the wheel if the brake cable snaps. On the front that could be very nasty, on the rear I'd have thought less catastrophic, though still upsetting for the rider.
Interestingly, my bike came with a straddle cable at the front and a link wire at the rear…