I'm not understanding how to handle comments exactly

Namely: rem &&Some comment~!@#$":<

This line has characters reserved to BrainFucks' operators. How do we transpile these comments to BrainFuck?

Context is important. In this context, only one variable was necessary. If two variables were necessary it'd make sense to leave them as two separate variables, and in that context I am sure most would make the appropriate decision that provides the best solution to optimize their performance, completeness, and simplicity of their codebase

Personally, I favor performance over readability because clients/users/customers do not notice nor value elegance as they do speed

I believe that without self it would not know what iterable object it was iterating over.

It is in our industry. Faster execution = happier customers

Reverse order != descending order. I suggest add a test case
31415926535897 => 9987655543321

This needs more best practices upvotes. Using the ternary operator to handle the base case and recursive case in one line. Well done.

..I thought the point of this kata was rewriting the upcase method?

How did you call .all? from within .all? and got an answer? It seems recursive when I look at it

This works, but this was one of my first solutions when I still pretty novice at Ruby. There's a few things I'd do differently, like try using an each loop for each char of the string and putting the ternary operator inside the block, but I wouldn't feel the need to write a gsub/regex solution. Part of coding in the real world is making your code readable to other people that you work with

Did somebody disable the use of a ternary conditional?

....I love this language

You should add what you want returned in the event that number is outside the range of Roman Numerals

Fair enough, guess I was overthinking