What cues or signs might make you wonder if a person is being sincere and genuine with who they are? can you tell if they're a phony?

I know some people are good at just detecting insincerity but what signs might make you wonder if they are really who they appear to be or if its all just some act they are putting on?

Here's some here. do you have any others?
What cues or signs might make you wonder if a person is being sincere and genuine with who they are? can you tell if theyre a phony?
What cues or signs might make you wonder if a person is being sincere and genuine with who they are? can you tell if theyre a phony?
What cues or signs might make you wonder if a person is being sincere and genuine with who they are? can you tell if theyre a phony?
What cues or signs might make you wonder if a person is being sincere and genuine with who they are? can you tell if theyre a phony?
What cues or signs might make you wonder if a person is being sincere and genuine with who they are? can you tell if theyre a phony?
What cues or signs might make you wonder if a person is being sincere and genuine with who they are? can you tell if they're a phony?
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