Imagine being in a bar, a party, or any social event full of people, some that you know more or less, many unknown.
Imagine that everybody constantly bump into each other because they all have one arm straight in front of them, with the hand like if they were begging for something. They would have only one hand remaining to actually do other things like drinking a beer, hugging friends, and so on. And before starting any conversation with another person they just meet, most of them would ostensibly put this open hand in front of their interlocutor. You would probably find weird to see all these palms in front of the faces of each other, but that would be probably because you'd be new in the place, as all the people around would act as if it was normal behavior.
When curiosity would get too strong, you'd start asking few people around you: "why do you keep your hand in front of you like that? That's not very practical, what's the purpose?".
And invariably, you'd get similar answers from all of them: "so if I was helpful in the discussion, you can reward me!", "hey! I've been nice to you? Drop me few cents!", or simply "Hey nice to meet you, give me a tip!". Often with a smile like this:
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Do I have to add that I don't get this thing with signatures? Do you act like that in real life? Very few people actually get "tips" here, and these people are really bringing something. When the first action of somebody with a new account is to copy this, it's very, very laughable to me.
