Overall, this was a cute episode. I like how Koharu got center-stage in a character-driven story. I thought the second half of the episode was pretty well done. We get to see empathy really shine through here just like in JN072. They can really do emotionally charged episodes well, and they created a compelling COTD to deliver on this.
The Frozen references were also nicely done.
There were a few things I didn't like, though. I thought Goh's presentation was kind of cringe. Of all the things that he could have talked about, he basically cranked the Ash flanderization knob to 11. Yes, it was an entertaining comedy routine, but it feels like an odd thing to start with considering this episode's theme. There is a very thin line separating friendly teasing and bullying, and it just kind of comes off weird.
That said, they could have done a lot worse here and gone overboard with "Ash worship." And I'm glad they didn't do that either.
I also agree with the criticism about the overall pacing. This seemed to neatly wrap up the bullying and the long-term effects it had on Regina in a single afternoon. Like many JN episodes, however, this would have been more powerful if it had a little room to breathe by spreading it across a few episodes. That's not unique to this episode, however, and there are many JN episodes that would feel more complete if they were spread across a few episodes. Especially since the episode's ending implies that Regina was able to grow through the adventures she had with Chloe, Ash, and Goh.
Finally, I'm not sure I agree with the view that the bullies were rewarded. I don't feel like they showed Koharu's classmates bullying Regina. Yeah, they were cold to her (no pun intended) because she was new and the incident with the Blizzard attack. But I don't feel like it reached the level they showed with kids in her previous schools. It could have definitely gone that way, though, if it wasn't for Koharu's friendship.
Overall, it was a good story showing Chloe/Koharu's development through a great character of the day.
/PS - Regina's art style kind of reminds me of Vladilena Milize from Eighty-Six.