1 year post FUE, is it safe to use a dermapen once a week at a 1-1.5mm setting? Would it damage the follicles?

At this point you will not injure any of the transplanted grafts. Additionally,the depth of the Dermapen needle is much more superficial than where the follicle is.

It is best to contact your surgeon for post surgery issues and care since all doctors have slightly different instructions.

Thank you for your question and photos
the number of grafts a patient will need depends on the thickness of their hair and the extent of their hair loss, which can be determined by the Norwood Scale below.
During a hair transplant, grafts are usually removed from the ‘donor area’ located on the back of the scalp and relocated to a balding area. The back of the scalp makes a good extraction area due to the high volume of hair follicles that congregate within that region that are not affected by the balding process. Specialist surgeons will remove a small amount of tissue that can grow hair and relocate it to the desired area of the head without damaging them.

At 1 year, the FUE grafts are in place, just like your other. You should get clearance from your hair transplant surgeon, but it should be safe!  Best of luck.

At one year after a hair transplant you are fully heald and normal and can do whatever you would have done prior to having the hair transplant