In my opinion, yes. I have been sitting on a Chiavari Chair for about 6 months in my office and I can say that it is promoting good posture and it is relatively comfortable.
Regarding comfort for extended use, I recommend using our chair as a desk chair yourself for a while to see how it holds up. In this way you will also be able to properly assess the comfort level.
Since the chair is made of wood, it is not entirely rigid and has some comfortable give due to the workings of a natural wood chair joint and also the curve of the chair back. Wood chairs with good joinery can allow for chair racking (back and forth movements) while still maintaining a strong structure. This is why a wood chair is more comfortable than a rigid metal chair.