"Robert Green" writes:

While I realize you're not condoning the practice, I've done that in the
past but now I use "clamps" designed to keep long cords coupled. The
reason? Tying the extension cords in a half-hitch causes the cords to bend
180 degrees where the wire exits either the plug of one cord or the socket
of the mating one. I've had the insulation break from the stress and reveal
the invidual wires.

You're not doing it correctly, then. Make the half hitch about a foot
below the plug/socket..