Most comments (and I've not heard that many) were along the lines of "are you coloring your hair?"
This is an interesting comment, because I've never had grey hairs (instead they fell out )
My hair has always been a light brown. My guess is that the comments have been made because the observer is seeing more hair and less scalp - hence more hair (and color) to see.
Also these comments are only made by folks who have not seen me in many months.
For those who I interact with daily - no comments whatsoever. It has been 10 months since my HT. One beauty of HTs is that the hair grows in very gradually. So, one you interact with frequently would likely not notice. There is no overnight transformation.
The same is true with losing, say twenty pounds in 6 months. A frequent contact might not notice anything. But, someone you've not seen in 6 moths would surely notice something has changed.
Having said all of this, potential observations/ reactions might vary according to your current NW classification. A "3" HT would probably be less picked up on than a "6" HT. I was a 4a.