In addition to Trent's technical chops, part of what allows me to accept his obviously conscious vocal mannerisms is how OTT they are and how the OTT nature mirrors his OTT lyrics. He sort of comes from the Jagger school of performing as more of an actor than a singer in the traditional sense (though he's obviously not on Jagger's level).
Glad you're diggin "The Spiral" brahski. Better late than never. And like I say in my review, the main appeal for me has always been the production. I put it on a short list of the best produced albums of all time, along with stuff like "Dark Side of the Moon", "Sgt Pepper" etc