as does my aunts 97.
that gauge is computer controlled. the computer puts it in the middle when the engine is in operating range. if the computer thinks its too hot, the gauge will start to creep up.
if its over half, the computer thinks its hotter than it should be.
its not like my 93s gauge, which is just a straight reading from the coolant.
hook up a scan tool if you can, and read the actual temps. that will tell the rest of the story.
the difference between aftermarket thermostats and the motorcraft thermostat is the size of the hole in it. the motorcraft thermostat flows much more coolant, and the the others just can't keep up. you need a motorcraft thermostat.