Are Chemex carafes microwave-safe, or will it explode (or otherwise get damaged)?
Short Answer: Yes.
Chemex (company) does not officially market their carafes as microwave-safe, nor do they officially endorse microwaving them. In addition, microwaving wood can cause it to desiccate, warp, or crack, so the most cautious approach would certainly not be to microwave the carafe with the wooden collar attached.
That being said, there has never been a report of a Chemex carafe exploding after being microwaved under normal conditions, and in general wooden dishware is commonly microwaved without noticeable damage. And personally, I heat my Chemex carafe (with wood collar still attached) in the microwave all the time, with no damage ever observed. (This presupposes reasonable microwaving conditions; i.e. no longer than 60 seconds at a time, and never making the wood collar painfully/dangerously hot to the touch. These limits should be sufficient to heat a typical Chemex carafe's worth of coffee from room-temperature to drinking-temperature.)