It's not so much if people comment, it's how they comment or avoid commenting. Both can be equally rude.
I have always been very active, but have taken up doing body pump/weights in the last few months, and I have been talking about this a lot, as I'm trying to encourage others my age to do weights, as strength building is so important for bone health and maintaining muscle mass. In the context of those conversations, or people who know my lifestyle changes, it's lovely to have compliments that reflect the efforts I have made. I have had lots of comments along the lines of I am looking slim alongside qualifiers such as also looking glowing and even people saying I look strong.
What is weird is if you have shared you are trying to lose weight and look noticeably slimmer, and people pretend you don't look any different.
What is rude is when people say things like "you must feel so much better now with all that weight gone", when I wasn't THAT big to begin with and they know I was still spending about 2 months of the year on walking holidays and climbing hills and mountains!
Others have said, I look great now, but always looked healthy before anyway (which is likely true, I am an hourglass that carried weight well, and didn't have a large belly, and always had large but muscular legs with no wobble).
It's also far too intrusive to ask how much weight I have lost or what I weigh now. That's just a no no. Like you never ask what someone's salary is. They are just forbidden questions.