Although I´m not an Operating System expert, and I´ve just started using OSX after coming from Windows, I consider myself a PowerUser in Windows, and fairly competent in Linux. Coming from that background, I´ve been surprised that in a fairly modern OS like OSX, the filesystem has quirks such as the way the names of files are "mungled".
I understand that Linus´ issues with HFS+ stem from the same point: from what I've found researching the issue, HFS+ stores the names of files using Unicode, but when a file uses "extended" or NON-ASCII characters (like á, é, í, ó, ú, ñ from Spanish or things like the ü in German), for which Unicode provides 2 ways of encoding the name, OSX silently "normalizes" the encoding at storage time... Not a real issue when the file has been created and consumed in OSX, but when you're sharing information with users of other OSs, the fact that the name of the file changes, makes for all sort of weird behaviours...
Case in point: I've been tracking my work "artifacts" (files, documents, etc) in Subversion for the last 8plus years. When moving to Mac, I got the SVN client for Mac, and after doing a Checkout of my relevant directories, I found that all files that have accents appear to be missing, and a new file with the same name appears as non-versioned. Digging into it, the issues is that the file IN the file-system is apple-encoded, while the data in the repository uses another (perfectly valid and legitimate) Unicode encoding...
This, I think, is a gross "mangling" of my data. Apple DOES understand both formats of the filename encoding (accessing a share in Windows, or using a USB stick from Windows shows the proper file names, etc) but at file creation time, it's decided "it knows better" and just renamed the files...
Again, not something most users will notice - until they make a copy of a file, or rename it, and put it back to where the original one was and end up with two files that are apparently the same!!!)