Not true. Instructors are only too aware of when they are required to write in a student's log book.
As for making a copy of a logbook but leqaving certain bits out and destroying the one with the comments written by an instructor - totally illegal. Is is a requirement to retain all logbooks for two years after the last entry.
Falsifying logbooks carrys a very high financial penalty of about £2500 per line!
Regards,
DFC
Not true either, a record of the flight must be kept for 2 years. Transferring to another logbook is not illegal, the requirements of keeping a record of the flight are met. Transferring to another log book does not constitute falsifying anything. If the book had become damaged you are within your rights to transfer the entries to another one or to a roll of toilet paper, napkin or matchbox. If you have a whim and want a different log book it is your choice.
The limits of what an instructor is entitled to write in a log book are a signature and licence number on successfull completion of a flight or nothing if a failure and remedial action required. It is not an Instructors right to deface someone else's property with red ink or comments.
If the owner of the logbooks agrees then they can make any addittional comments by mutual consent. I along with many others on here have a whole load of comments from instructors and fellow pilots that enhance the memory the log book contains.