And: you assume that SIP-URIs are always enclosed in <> when there's a parameter appended. Where do you take this assumption from?
Where did I make this assumption? It is wrong, having no <> is correct and follows the RFC. But in this case, the display name must not be present.
Except Route headers. In Route: headers the SIP URI must be enclosed in <>. Further, if the paramter is a URI parameter, the URI must be enclosed in <>, otherwise, the parameters will be header parameters.
regards, klaus