Not sure what I did wrong here, any help would be appreciated.

The patch seems reasonable, but I wonder if we could more actively guard against recursion here? The main problem is that StackOverflowError can often happen in the middle of sensitive code, like building up some internal parts of a data structure. That makes those errors (and the SystemStackError we re-raise) generally fatal, since you can't rely on the state of the system.

Take another look at the MRI code in this patch, from the MRI bug I referenced in #1111: https://bugs.ruby-lang.org/projects/ruby-trunk/repository/revisions/43208/diff/compar.c

Roughly equivalent code for us would be Ruby.recursiveListOperation and execRecursive, which you can see used for RubyArray.join19 logic. Have a look at that and try to do the same sort of recursion guard in RubyComparable.

Thanks for jumping in!

Closing since new version of PR exists