I recently bought a used Polar Frost Knife from the merchant board. At the time I bought it, the durability was 0/118. I therefore expected to be able to repair it to 59/59 and get some fun out of it before buying a 'repair hammer'.
However, the repair screen at the blacksmith did not show this knife as an item I can fix. I had to go straight to the repair hammer. After the repair it's back to full health and still not showing in the repair screen as a 'normal' weapon would.
If laser weapons are non-npc-repairable then that's fine, I understand why it does not show up, but that does not explain the durability on it when I bought it.
Is there a simple explanation?