alt Hacker NewsWriting twice makes sense if time permits, or the opportunity presents itself. First time may be somewhat exploratory (maybe a thow-away prototype), then second time you better understand the problem and can do a better job.
A third time, with a new abstraction, is where you need to be careful. Fred Brooks ("Mythical Man Month") refers to it as the "second-system effect" where the confidence of having done something once (for real, not just prototype) may lead to an over-engineered and unnecessarily complex "version 2" as you are tempted to "make it better" by adding layers of abstractions and bells and whistles.
I agree with what you're saying about writing something twice or even three times to really understand it but I think you might have misunderstood the WET idea: as I understand it, it's meant in opposition to DRY, in the sense of "allow a second copy of the same code", and then when you need a third copy, start to consider introducing an abstraction, rather than religiously avoiding repeated code.