It depends on the horse... I have never personally done it, although have known people who do. One horse I would do it on would be my mare when she is retired (long time off yet).
This year, because she is in foal, she has been left to grow a coat. She gets quite warm at night in her stable, and can get a bit aggitated by it (gets itchy and cross). When she is retired (she is only 10) I think she will require clipping to keep her happy and allow me to rug her up so as she is not getting cold joints etc.
I have been asked THREE times today when I am clipping! Errrrr I came back from an hour's hack with only slight girth sweat, I jumped and schooled on Sat and had minimal sweat - why WOULD I clip?!
I do tend to full clip my cobs out at the end of February to have nice summer show coats for April.
If I don't do this, I still have very hairy beasts to the end of May moulting everywhere.
I also find they are happier for it, as they don't stand sweating on a warm April day.
I do clip out my boys even though they are in light work as they get hot even with 10 minutes walk. Cairo has a blanket clip but with the hind quarters left on and Chancer has a chaser clip as he is only long reining and doing a little work on a lunge line - but he will be dripping after a short session of walk and trot. I also exercise late in the evenings and have to have a dry horse before I leave which is not possible with them in their full woolies.
Assuming this is a RL scenario, you may want to remind the said person that the appearance will go unnoticed! I mean, if it's not being ridden, surely it will have rugs on all the time!