A grand achievement of some sort, whether it be a medal, a title 'upgrade', or some form of big acknowledgement from the King could've suffice and fit the narrative you provided.
The issue I had, when it comes to a writing standpoint, was that it was her appearance that was changed. Something that you have absolutely no control of whatsoever. Isn't the entire trope of this reincarnation/isekai genre is to show the loser turned God through their hard work? That theme is integral to stories like these, and what the author chose to do just works against it. Readers are supposed to cheer for their MC through the struggle and change.
Borrowing from what you've just said, here's what I think would've happened had the author actually had that reasoning in mind. After the Light Goddess changes MC's appearance, MC feels unsure immediately. She then debates on why she wasn't feeling exactly happy about the gift she received. Right before that realization could hit, her mother invited her to talk and apologize for her poor decision. That's when it hits MC- that the Light Goddess had the galls to change MC's appearance without putting consideration in what it truly means to her.
But we all know this isn't the truth. The author decided to bring back MC's appearance, as in act like it had never happened in the first place, because of the backlash from her Japanese fans.
Now, onto the moral standpoint. I highly doubt the author wasn't aware of the implication of their choice. The discrimination against POC is literally in news media every other week, popular enough to reach all the way to Japan. And for those that are like "#AllLivesMatter, white people also get hurt!!!" It doesn't matter where you stand on that, what matters was that there's practically no benefits for either the publisher or author in her appearance change, and the fact that she was changed back later on meant they most likely regretted their decision.
I can't think of a single valid reason as to why the author chose to make this change.
It's mind boggling, and this will be my last comment in regards to this topic.