On further investigation, the issue is the "Prefer display name over message header" preference for each contact. Testing on a new contact, it is defaulted to OFF when added to Collected Addresses. I guess this patch now respects that pref properly when the code did not before, however due to the above behaviour many profiles are going to have an address book full of improperly configured contacts that will change the observed behaviour.
Bug 243258 Comment 99 Edit History
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On further investigation, the issue is the "Prefer display name over message header" preference for each contact. Testing on a new contact, it is defaulted to OFF when added to Collected Addresses, even in current Daily. I guess this patch now respects that pref properly when the code did not before, however due to the above behaviour many profiles are going to have an address book full of improperly configured contacts that will change the observed behaviour.