Can an Alfine 11 replace a Nexus 8?
As @Kibbee has stated the IGHs do have a different OLD, although Nexus hubs can be spaced out to 135mm with spacers/ bolts/ washers.

You need to measure the Dahon's rear dropout spacing.

I can't find anything to suggest otherwise so I assume it's 132mm, in line with other commuter type bikes.

The limiting factor is dropout spacing. The Dahon is an aluminum frame with short chainstays. Both of these essentially prevent the ability to spread the dropouts and force a wider hub in. Aluminum is brittle and not malleable like steel, it doesn't like being bent.

You may damage your frame and void the warranty.