Ignore def doesn't stack

Maybe I missed something, but I don't understand the outcome so I gotta ask a few questions:

1. Ignore def does not stack on the same weapon (like 15% and 30% being on the same wep wouldn't stack)?

2. Ignore def does not stack on the different weapons (like 15% on a dagger and 30% on a katara wouldn't stack)?

3. What about 15% on a codex to 15% on a weapon, doesn't stack either?

>haven't tested it myself, but suppossedly stack

>haven't tested it myself, but suppossedly stack

>they would probably stack, however the codex doesn't even give the 15% ignore, so in this example all you have is 15% on your weapon