Case-insensitive ext4

I think by System 7.5 (or 7.1 Pro) you did, because if I recall correctly that's how File Exchange/PC Exchange did its work.

Remember, in classic Mac OS the colon ':' was the directory separator in paths, and you could use '/'s to your heart's content. Actually, you could use pretty much anything to your heart's content, including spaces, punctuation (since no one in the Mac side cared about extensions) and even weird graphs like the f-hook or florin https://en.wikipedia.org/wiki/%C6%91#Appearance_in_comput... , which I still find myself occasionally doing on OS X 20 years later.

Anyway, with /. \. and : being used in different locations, there was definitely path-mangling going on below the interface. But general users didn't have to care, and most Mac programs didn't deal with constructed path names, and *never* had to worry about shell-quoting for spaces and whatnot.

Between this freeform text attitude, the resource and data fork dichotomy, and the use of Type and Creator codes, I definitely feel like we've lost some good capabilities on the Mac side in the quest for broader interoperability.