It is a complete mystery to me why it has been said that the use of manual trim is "discouraged". The issue is one of many which requires examination in the manner described by Lonewolf_50, (quoted above), Chris Scott, Machinbird, gums and others. (The Final Report will indeed be very challenging to write.)
Simplified, in Normal and Alternate Laws, movement of the trim wheels disengages the autotrim function during wheel movement but re-engages the autotrim when movement stops. The trim will move back to a position ordered through the AFS [Auto Flight System], which, as stated, is 'gee-driven', again, very simplified.
PJ2, your description of the manual pitch trim was my initial understanding of how manual pitch trim works.
That once you let go of it, the system would again move the trim to where it wanted to move it.
Others have stated that once you handle the manual pitch trim, it stays in manual for the duration of the flight and has to be reset on the ground.
May as well sort out this detail fully. If you remained in manual THS, it would have implications for proper flight control function on some of the "protections."
Are there some old wives tales running around here, or possibly differences between aircraft types?