fix up

proposals/2229-rebind-existing-3pid.md

@@ -1,20 +1,25 @@
 # Allowing 3PID Owners to Rebind
 
+```
 3PID
     noun
-    A third-party identifier such as an email address or phone number, that
+
+    A "third-party identifier" such as an email address or phone number, that
     can be tied to your Matrix ID in order for your contacts outside of
-    Matrix to find you, typically with the help of an [identity
-    server](https://matrix.org/docs/spec/identity_service/r0.2.1.html).
+    Matrix to find you, typically with the help of an identity server.
 
-As part of the on-going privacy work, Matrix client applications are
-attempting to make the concept of an identity server more clear to the user,
-as well as allowing a user to interact with multiple identity servers while
-they're logged in.
+Identity server
+    noun
 
-As part of facilitating this work, Matrix clients should be able to allow
-users, while logged in, the ability to pick an identity server, see what
-3PIDs they currently have bound to their Matrix ID, and bind/unbind as they
+    A queryable server that holds mappings between 3PIDs and Matrix IDs.
+```
+
+As part of the on-going privacy work, Matrix client applications are
+attempting to make the concept of an identity server clearer to the user, as
+well as allowing a user to interact with multiple identity servers while
+logged in. In facilitating this, Matrix clients should be able to allow
+logged-in users the ability to pick an identity server, see what 3PIDs they
+currently have bound to their Matrix ID, and bind/unbind addresses as they
 desire.
 
 When implementating this functionality, a technicality in the spec was found
@@ -23,14 +28,14 @@ The line "The homeserver must check that the given email address is **not**
 already associated with an account on this homeserver." appears under the
 [POST
 /_matrix/client/r0/account/3pid/email/requestToken](https://matrix.org/docs/spec/client_server/r0.5.0#post-matrix-client-r0-account-3pid-email-requesttoken)
-line. The same goes for the [equivalent msisdn
+endpoint description. The same goes for the [equivalent msisdn (phone)
 endpoint](https://matrix.org/docs/spec/client_server/r0.5.0#post-matrix-client-r0-account-3pid-msisdn-requesttoken).
 
-If a user binds their email address, through the homeserver to identity
-server A, then switches to identity server B to try and do the same, the
-homeserver will reject the second request as this email address has already
-been bound. This is due to the homeserver attaching the email address user's
-accounts whenever a bind is performed through them.
+When a user binds their 3PID through a homeserver to identity server A, the
+homeserver keeps a record and attaches the address to the local account.
+Then, if the user switches to identity server B to try and do the same, the
+homeserver will reject the second request as this address has already been
+bound.
 
 ## Proposal
 
@@ -38,13 +43,14 @@ This proposal calls for allowing 3PID owners to rebind their 3PIDs using the
 [POST
 /_matrix/client/r0/account/3pid/email/requestToken](https://matrix.org/docs/spec/client_server/r0.5.0#post-matrix-client-r0-account-3pid-email-requesttoken) and [POST
 /_matrix/client/r0/account/3pid/msisdn/requestToken](https://matrix.org/docs/spec/client_server/r0.5.0#post-matrix-client-r0-account-3pid-msisdn-requesttoken)
-endpoints by extending the definition of what homeservers should check before rejecting a bind.
+endpoints by extending the definition of what homeservers should check before
+rejecting a bind.
 
 Homeservers should reject the binding of a 3PID if it already been bound,
 **unless** the requesting user is the one who originally bound that 3PID. If
-so, then they should be able to bind it again if they choose.
+so, then they should be able to bind it again and again if they so choose.
 
-In doing so, it would allow users to bind their 3PIDs to multiple identity
+In doing so, users would be able to bind their 3PIDs to multiple identity
 servers, even if the homeserver has already been made aware of it.
 
 ## Tradeoffs
@@ -63,6 +69,10 @@ Clients should be prepared to understand that this may just mean they are
 dealing with an old homeserver, versus the 3PID already being bound on this
 homeserver by another user.
 
+Homeservers will need to keep track of each identity server that an address
+has been bound with, and upon user account deactivation, should attempt to
+unbind all of them.
+
 ## Security considerations
 
 None.