From what I understood a CHARACTER (not a PERSON) cannot contribute to multiple guild's progression, but their alts could do so in other guilds.
Seems like we have two different scenarios being argued here...
The issue with Hatred's kill was that they had someone who wasn't in their guild at the time of the kill.
The supposed issue with Intrepid's kill was they had a raider's alt who was used in another guild's clear.
Clearly two very different issues.
Seems like there is nothing wrong with Intrepid's kill, as it is an alt. By the logic I'm seeing above, would you all want to take Raze's progression into question? Beastfury uses an alt there.. See, makes no sense.
I don't care either way to be honest, just thought some non-bias viewpoints would be appreciated.