Let me add to the chorus of "no lounge re-entry stamp required"; and share a cheeky stunt I pulled.

Was flying a rather convoluted CX J ticket that involved a CMB turnaround. Passing through HKG, I was guested into The Wing - F Lounge, by a friend who's OWE. Used the lounge service desk to get myself checked in for the flights originating in CMB and then, on the way out, got the next day's ex-HKG boarding pass stamped with a F Lounge re-entry stamp.

Worked quite well to get into The Pier F Lounge, allowing me to use one of the private rooms to catch up on sleep while Wx delay pushed my onward flight back by 3 or so hours.