I just see this as a passive-aggressive attack on everyone who lowmans events these days with a mule or pet. He probably got camped on in Dynamis or something.

People who duo with mules pay twice as much per month and make a little less than twice as much gil per month, but they invest less than twice as much effort to make it and it takes the same amount of time. Mules are essentially just a fast forward button. If it is worth it to you, make one. If it is not, don't!

Either way, making passive-aggressive threads on the forums reminding people (specifically with mules) to play nice is kind of futile and misguided. In the last six months of dynamis, I definitely saw more single-character players committing dynamis faux pas than mule-owners or BSTs. I bet about half my runs in Dynamis - Tav end when parties of single players fail to check my very explicit search comment and show up only to realize I am clearing the relevant monsters on upper floor duo with my mule. Then they sit there getting 3/10 clusters breaking my rhythm probably complaining to each other about my mule and me.