Thanks for all the replies. Sounds like a case of Your Mileage May Vary; a 6.5 A1C might cause damage and a 7.0 might not.
Regarding the fasting blood glucose, the acceptable range is generally given as 80-120. So 100 is right in the middle of that range, and is just fine. Slightly higher than that, up to 140 is OK for some diabetics, especially if they are prone to low blood glucose.
I’ve been told that cell damage starts to occur when it’s over 200.
You’ve been told wrong (see pretty much all of the links throughout this thread).
200 mg/dL is about 2.4X the blood glucose level of a healthy person and is equivalent to an A1c of 8.6. Plenty of damage can occur at that level.