A small point, but it really p*sses me off when the callsign changes but the three letter identifier does not.
Causes no end of wrong use of callsign for a good few weeks until the ingrained habit gets erased.
Happened most recently with Top Jet/Kestrel (TCX) - some office bods who retain validations are still getting that one wrong because they havenot had that much exposure to the new (almagamated) callsign yet.
How hard can it be to change the identifier as well? I know we are supposed to be professionals but when we use the identifier with a particular callsign for years, it's a difficult habit to break.
In the grand scheme of things it's not a biggy, but it's an obvious thing that could be fixed and is one less link in a potential chain of events