Do you have evidence of this theoretical "person who buys games just to troll"? Because you do know that anyone came simply link a picture of gameplay with Shantae on it but you can't do that with a Switch interface.
That is why the burden of proof before going on said support list should require you to show that you have played said game. Oh and once again to show that I am not again just saying "do something I wouldn't do" type of thing:
So yeah I am not telling people to do something I myself would not submit myself to do to prove I am a supporter.
My point was that you can't make sweeping generalizations about others who may want to show support just because they can't "prove" to you that they've played a Shantae game.
And no, I don't have an example of someone buying games just to troll, because for one, that's not what I said, and even if it was, the point would still stand.
Addressing your point: If they really wanted to, a troll CAN buy a Shantae game and provide their proof to you only to show their true colors later, in which case your paranoia and attempted gate keeping will have failed you.
And my point while similar was one where an actual fan decides to troll you because while they do like Shantae, they also happen to like trolling. In which case the scenario would play much in the same way and your gate keeping would still fail.
Moreover trolls don't even need to masquerade as Shantae supporters, if they're going to come trash talk us, they're going to do so anyway.
We don't need to and shouldn't require people to show "proof" of their supposed brand loyalty, because simply buying a game means nothing. Again, not everyone who bought a Shantae game is a fan, or attached enough to the character to want her in Smash.
Moving on to the Switch's interface. What about people who don't own a Switch? Are screenshots not from the Switch's interface, not proof enough under your supposed means of keeping trolls at bay?
The logic stemming from your paranoia makes no sense, and any attempts at gate keeping will not only fail to deter trolls in any way, but instead will be a detriment to Shantae supporters.