While writing the code I was expalining it to a friend he asked questions I then answered with the comments.
In retrospect, it is a bit too much, you are right. I need to learn how synthesize my thoughts better.

Either way, thank you very much for your feedback, and for reading my code.

Good point. This solutions does not correctly handle upper camel case.

The test_solution_randomly function strips the uppercase letter from the start of the sentence with:

            sentence.push_str(&word_selection.next().unwrap()[1..]);

So I take it this problem is only intended for lower camel case.

The problem statement should probably be made to be more specific.

I see someone already reported the issue:

https://www.codewars.com/kata/5208f99aee097e6552000148/discuss/rust#6181ac3bac59440057e75f57

Lol I don't blame you. It is very confusing, even to myself when I'm trying to understand what I wrote a year ago.

I would never write this kind of code for production. What happens on CodeWars stays on CodeWars or something, I guess.