Is there a particular reason why Haitian people repeat everything you say to them? Is it because they want to make sure they understand what you're saying?

I don't think every Haitian does that.
Perhaps, like you said, if they're talking to a foreigner they might want to make sure they understand what's said.
I sometimes do that with foreigners.  If one word in their sentence is wrong, I repeat what they say to correct them... with a smile :)

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