EDIT: correction. Using address seems to only work when address has been used in blockchain and pubkey can therefore be retreived from blockchain
I've now tried it, myself:
I picked a compressed and an uncompressed key from my wallet (yes, my wallet
has a couple of each kind) and created a multisig-address from these two.
I then re-did the addmultisigaddress, replacing the compressed address
its compressed key
, and it gave me the same multisig address back as before.
Then I re-did it again, this time with the "04..."-format pub key
without much surprise I got a different address, now.
matters, whether the address has been created as a compressed or
uncompressed key, and the current feature is very bad
at the moment when
used on compressed addresses!
If some key is a "compressed" one, and you pass that "04..." string to someone else,
who then creates a multisig-address based on the "04..." key you gave him, then you
will NOT be able to sign it later
For compressed keys, the blockchain.info wallet should definitely show some "02..."
or "03..." string!
EDIT: has been fixed, since. Thanks!