A compressed address/private key combination cannot be "decompressed" for any useful purpose; a decompressed private key (which only has a flag indicating that the public key is uncompressed) has a different bitcoin address.
Some clients, notably Electrum, do not support compressed addresses (which may result in you paying more fees than you need to).
oh...if that's the case, is there any way to export the "original" private key from Multibit? The one that starts with a 5?? So that I can restore my wallet to any client in the future without any worries?
Only if you want to not be able to spend your money, read what you quoted.