In reply to your bullets, fully agree. The definition of identity in your description is the tie between an account and a physical identity. Anonymous accounts have a form of identity, to allow their reputation to build, but they don't have the tie to a physical identity. Twitter has Verified account method of tying account to physical identity. Maybe "verified identity" is a better term for your definition of identity.
In many cases, publicly known links between an account and a physical identity are undesirable, hence the support for interacting with fully anonymous accounts. In other cases, someone may want to rapidly build their "reputation" for a given account, so they go through the "verified identity" process for that account, which could give instant "reputation" value.
"Reputation" management systems could vary by platform, but displaying reputation value for a given account makes the "ipsn" more valuable, to help users sift through the information flow more effectively. The idea of one reputation upvote/downvote per user per day for a given account is just one possible implementation of a reputation management interface.
Agree on the official institution method of verifying identity, e.g. certification organization. This part of the discussion would be best served on another discussion thread and include sovereign identity protection concepts.
On reputation building rules, "reputation" can follow account, but in today's world, each social media platform has its own account universe. The "Login using FB" or "Login using Twitter" are some schemes to allow you to carry your account with you to different platforms. Maybe a universal "ipsn" account with associated "reputation" and/or "identity" could provide value when a user traverses different implementations of "ipsn".
When we start discussing identity, voting, etc, with both anonymity and non-anonymity, the implications become broader than just a social network. Other parts of the village come into play, e.g. contracts, conducting business, in addition to having conversations.