I have search for the necessity of using only compressed Public adresses and compressed private keys on the spreadcoin website and in the white paper but I can't find it!
Mr. Spread (the original creator of Spreadcoin) implemented this as part of his "compact transactions" scheme.
Oh I think the community is fine.
No miner, no exchange, no user of official spreadcoin software ever complained about the compressed key format.
Sadly it's always the zero-post accounts that pop up now and then who used some third party service (that we don't recommend for a reason) and then they complain.
All I can do is make the warnings bigger I guess.
Well, de facto, since Spreadcoin doesn't use non compressed keys your spreadcoins are NOT part of the Spreadcoin blockchain.
And yes, I understand that the amount you sent is clearly visible on that SPR address, but you DON'T own the compressed private key that corresponds to that address.
Basically, you sent your SPR to the wrong address.
I know it sucks but those are the internal rules.
No, we can't have both compressed and uncompressed keys, since that would amount to 1 privatekey controlling two kinds of spreadcoin addresses, and all SPR amounts would be double, that's not how this works.