Should the sdcard support case-sensitive files?
Android itself is based on Linux, which is designed for case-sensitive filesystems. Internal storage is usually on an ext or ext4 filesystem, which is case-sensitive. SD cards are usually formatted with FAT 32, which is a case-insensitive filesystem. Although Android can support using other filesystems on the SD card, Windows PCs can't, so it's unusual to format your SD card with a different filesystem, and if you do this, you can't use the SD card in a Windows PC (via a card-reader), nor can you have the phone act as a USB mass storage device when connected to a PC.