You keep bringing this up like you're phenomenally proud of it, and telling people this will make them recognise you for the charismatic genius you claim you are.
What it makes me think, every time, is
what the heck did these exchanges look like from the other person's point of view?
Did the person feel hassled by you? Intimidated? Did you hang around telling them how everyone else thinks you're wonderful and gives you gil out of the goodness of their hearts and the power of your persuasiveness, so why won't they hand over theirs?
If so, then they are not doing it because you've convinced them through your "superior" social skills. They're doing it because they want you to leave them alone.
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I also find it hard to believe that people will join-and-leave your FC with
only the conversation you described, unless it's because they're seeing the FC is totally dead and they'd rather find one that is more alive. (Or possibly they're the sort of people that join and immediately go to see whether the FC chest is unlocked.)
But is that really
all that's said between you to cause them to leave? Or is your "time spent nurturing loyalty" (as you mentioned in the next paragraph) what's actually scaring them off?
Because we've discussed this before.
Repeatedly.
Over and over, you post about your ailing FC and how people won't stay in it. You get replies explaining that actually your displayed personality and approach to the situation might be having the opposite effect to what you want to achieve.
And then a month later you make another post showing the exact same attitude. "I'm doing everything right, why will nobody stay? Why the disloyalty?"
So, I've said before: stop talking about people like you only care what you get out of them - whether what you want is loyalty, gil, or their continued presence so you can be proud of your large, thriving FC.
Stop assuming you have wonderful social skills and charisma.
And for goodness' sake,
stop telling everyone how much people are willing to give you gil for free.