Full Stack MERN Application, Mobile-first Design

It would be an understatement to call this challenge hard. It took me a while to figure out how to do the frontend and even more time to figure out how to hook it all up with the backend. However, I did have a lot of fun with this challenge and I learned a lot from it! With that said, I still have some confusions or things I'd like to hear advice about.

1. For the frontend, I decided to export all functions my components would use into a separate utils so that my component functions would only contain the states of the component and the render method. Is this good practice? I wouldn't consider my organization the best since I'm still relatively new to this so I'd love to hear some feedback!
2. I noticed that the desktop and mobile design of the comments had very different layouts so I decided to create one component for the mobile version of the comments and one component for their desktop versions. Was this a good call? This is my normal approach and it usually works fine but my implementation of the comment component was very lengthy so I noticed a lot of the time I was more or less copy-pasting code. Any suggestions for improvement?

Any comments regarding answers to these questions or any feedback is greatly appreciated. Many thanks and cheers! 🎉