Great question — answering as the UphillTech team:
The filament is there to add strength to the cord. Everything else stretches more than the poly-fiber so when you pull on it(the cord) it strains against the fiber instead of the delicate electrical connections. As far as splicing it goes...you could tie a knot in it if there's enough slack or just ignore it and be careful with that spot in the future. And keep your cat away from it:)
Full answer by user23534: https://diy.stackexchange.com/a/53285 (CC BY-SA 3.0).
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