On gnuplot 4.6.5 on an x86-64 RHEL-like system, I see
$gnuplot
gnuplot> set term x11 persist
gnuplot> plot sin(x)
gnuplot> exit
leave a persistent window as expected while
$gnuplot
gnuplot> set term x11 persist
gnuplot> set termoption enhanced
gnuplot> plot sin(x)
gnuplot> exit
does not. Curiously,
$ gnuplot -persist
gnuplot> set termoption enhanced
gnuplot> set title 'Foo_0'
gnuplot> plot sin(x)
gnuplot> exit
works and the title confirms that enhanced mode is working here.
Original mention: https://sourceforge.net/p/gnuplot/mailman/message/32079563/
