For a while now, there has been a slight disparity on the armoring, hilts, and barrels between the types of play. Today, BioWare announced that changes are coming to the system to fix the issue in the future.
Quote from Allison Berryman
I talked to Senior Game Balance Designer Jason Attard about mods that are bound to slots and our plans for them. Here are some comments he had about the system and its future:
Many (but not all) of our current endgame Armorings, in both PvP and PvE, are bound to specific slots. This is because some less expensive items, like gloves and boots, are much easier to acquire than "expensive" items like a Chestpiece or Helmet. We've seen that instead of acquiring an entire set of gear players would often purchase the "cheap" slots multiple times and simply move the mods over into the "expensive" items, allowing players to acquire their gear much more quickly than intended. Now that most of our offhand items have mod slots we are seeing a similar pattern occur with main hand and offhand items.
We plan to make these slot restrictions more consistent in the future, with any Armoring, Hilt, or Barrel you extract from an item becoming bound to the equipment slot you extracted it from. We do not intend to add the same slot restrictions to Modifications or Enhancements, as those item mods have a smaller impact on the overall power of the item.
For the thread in full, visit the official forum.