Are you the Civic’s original owner?
Is the PCV valve mounted vertically?
Are you sure it isn’t upside down?
PCV valves do have loose center pieces. In their static state they allow free passage of gasses from the area under the valvecover to allow the crankcase gases, which propagate up to the area under the valvecover via the return passages to the crankcase, and only minimal passage of gasses from the engine’s intake to the space under the valvecover to prevent any backfire from igniting the gasses under there, which may be saturated with hydrocarbon byproducts. The weight of the PCV valve’s center piece is low enough to allow pressure differential between the intake and the area under the valvecover to raise it and allow the free passage of the gasses, yet heavy enough that without a pressure differential the center stays down (closed), protecting the crankcase gasses from undesired ignition from a backfire.
Conditions that can cause a PCV valve to rattle are improper installation (upside down or not vertical), or erratic pressure differential fluctuations between the intake and the crankcase. The former can be checked by simply looking at the arrow on the PCV valve… it should opint toward the engine’s intake. The latter possibility can be easily investigated with a simple pressure/vacuum gage. If it exists, and the rattle bothers you, things that affect this such as valve backlash, compression, and such can be investigated further.
Post back. I’d like to work through this one with you, with help of course from the real experts here.