SAP user type Communication versus System and impacts

Dear all,

I know that user type communication (C) are no more used in SAP systems. Now we have to use System user type. (B)

http://wiki.scn.sap.com/wiki/display/Security/Best+Practice+-+How+to+analyze+and+secure+RFC+connections

1. I am searching for a SAP note or SAP recommendations document explaining this. Could you tell me where I can find this ?

2. For me, there are no impacts to change all users from user type Communication to user type System. Could you confirm ? In all knid of system version?

Thanks and regards,

Mélanie