Filesystem case sensitivity
I got a couple of nice replies to my question. Everyone agreed that filesystems preserving case made sense, but people seemed to be skeptical that case sensitivity was a good thing. The strongest statement in support of case sensitivity so far is that it provides the flexibility to implement both case-sensitive and case-insensitive systems and software on top, in another layer, whereas case-insensitive filesystems don't provide the flexibility to implement case-sensitivity (in that software will never be able to create a file called "polish" and another file called "Polish").
The deeper controversy, briefly addressed by one correspondent, is probably whether it makes sense for software to expose filesystem case-sensitivity to a user. I may have been making an unstated and possibly unwarranted assumption that the view of a filesystem in an API (for example, in the Unix open(2) system call) is the same view which will appear in a UI. This has traditionally been true in almost all Unix software, but not, for example, on a system like MacOS. It is possible to have a filesystem which is case-sensitive but a UI which conceals that case-sensitivity -- or even does more, e.g. translating UTF-8 in a filename into Unicode glyphs, and vice versa.
