I've been in many situations when players with bonus join farm parties.

What you will usually get from them:
- This is my alt, cleared it on my main.
- I've see it to 10% and looking for a good party to kill it.

For me, I go easy on with these people because they might be telling the truth. I give them a chance to prove to me and rest of the party that what they said is true.

Recently I had this happen and one of the party members got very mad saying that players should respect the PF rules. Since my party was a farm, everyone must have a clear. And for all we know, that player might be lying. Resulting in wasting everyones time.

If only we had an option to allow people who cleared a certain fight to join. It will solve this issue for sure.