Tested and confirmed on 6-27-15 that when generosity sigil transfers a thief’s poison while the thief is traited into Deadly Arts due to the trait “Lotus Poison” the trait works against the user and transferred poison also applies weakness.
This test was done with Zeromis’s mesmer. I used choking gas to apply poison and when he transferred the poison back with generosity sigil weakness was applied to me as well.
I’m guessing though I haven’t tested it — that this bug also applies to other traited conditions.
I was not aware of this bug before the patch but it’s likely that it existed before.