Hi,
I had this on mine – perils of buying a secondhand frame… Anyway, chaps at Orange were adamant it could be helicoiled and it was nearly on its way to them when I tried a much simpler solution. The stock bolt on mine was about 30mm long (giving about 10mm of thread engagement) so I tried a 45mm bolt. Turned out there was a lot more thread in that hole than was strictly necessary. Worked just fine, and that was about two years ago now. I am very careful with the torque on that bolt, though. Orange recommend about 14Nm (IIRC), I use 10 and that does the job.
The original thread damage on mine wasn't too severe, though – partially stripped / rounded rather than stripped bare.