+1 for Lendal paddles. I have a 4-piece carbon Lendal that I have been using as my primary paddle for over ten years. I bought it as a spare/travel paddle, but found that I like it better than a one-piece. It has taken tons of abuse and is holding up just fine.
The 4 pieces lock together as Leland explained upthread, and it makes the shaft absolutely rock solid. I have a 4-piece Werner I use as my spare and I HATE that paddle! Those little pop up buttons that connect the shaft pieces are so loose and wiggly. It feels like the shaft is always ready to fall apart on you. Drives me nuts.
Another advantage of Lendal's locking system is that the feather and handedness can be changed and locked in place very easily. So if you give your paddle to someone who just lost their's in the middle of a run, they can set the feather to what they're used to and not whiff a brace or stroke.
Lendal is a Scottish company and was purchased by Johnson Outdoors shortly after they bought Necky kayaks. (early 2000's, I think.) At some point, Lendal got spun off on its own again and, as far as I could tell, quit making WW blades, just blades for surf and touring. And there was no distribution in the US. But thanks for the tip re: Celtic paddles, as they appear to use the same locking tech and also offer WW blades. And the price isn't too bad either, since the British pound tanked following the Brexit vote.