Most of the interesting recurring species and cultures have evolved from aliens-of-the-week. Many have managed to do that without obvious contradiction (say, Romulans, Klingons, Bajorans, Cardassians), while others have kept evolving so much that it's not possible to point out a single specific contradiction or a single badly handed step, merely a continuum of change (Borg).
The Trill didn't evolve all that much after being reintroduced in "Emissary". We got the fancy ritual of remembering past hosts, but that was pretty much it. Being so weird to begin with, the Trill might well have warranted further weirdness that would have obscured the initial change from "The Host" to "Emissary"... Plus a bit of makeup diversity (such as what we got with Romulans and Klingons) to alleviate the change in appearance. We now readily believe in a broad range of acceptable Klingon faces; we could have gotten spotted, striped and plaid Trill just as easily.
Timo Saloniemi
The Trill didn't evolve all that much after being reintroduced in "Emissary". We got the fancy ritual of remembering past hosts, but that was pretty much it. Being so weird to begin with, the Trill might well have warranted further weirdness that would have obscured the initial change from "The Host" to "Emissary"... Plus a bit of makeup diversity (such as what we got with Romulans and Klingons) to alleviate the change in appearance. We now readily believe in a broad range of acceptable Klingon faces; we could have gotten spotted, striped and plaid Trill just as easily.

Quite so. I just thought this would have been a fun juncture to flaunt Curzon's former status - and it's the moment that probably comes the closest to establishing anything at all about said status.Jadzia isn't entitled to diplomatic status just because Curzon was. They are different individuals under Trill (and Federation) law.
Timo Saloniemi