You're instructing PM to make modifications to the file when you tag it. The modification time is updated. This is useful for backup purposes.
Why not use Capture Time sorting instead?
Thank you for this immediate reply. Well i tried Capture Time sorting but it's very slow - maybe caused by my antique laptop. Somewhere in this forum i read that sorting by mod. date is faster. My whole picture system is based on date. The originals are kept in one folder, processed pictures seperate. Therefore i like to keep the nefs in the order of the shooting. I used tools > adjust... to get everything back in order.
At least for my workflow tagging is not of importance for any backup. I ingest into a folder, review and tag, then copy all pictures i keep in my camera folder. That's it.
Interestingly now i can tag and untag, refresh and the sorting doesn't change, no matter which contact sheet is opened. Strange - now PM is behaving differently....
oliver