I think that the general idea is that either you're guessing at the appropriate representation of the testifying users, or that they've picked those emoji. If the latter, then all is good! If the former, then it's generally a bad idea to assume that you know something about a person based on their name, or even, really, anything other than their implicit election. (I would certainly be upset if a business to whom I had offered a testimonial used it and misidentified me, even in ways that may seem trivial, especially if they could have just asked me.)
I assume that was sarcastic, but why not? Do you have any right to choose the emoji to identify me? I mean, you surely have every right to editorialise with an emoji that you think reflects my behaviour, but, if you're going to quote me below a symbolic representation, then I think it's different. If one has to use an emoji to identify someone—and it's not at all clear to me that it's necessary—then, after all, we're talking about who has reached out; why not just ask them?
(For example, surely—right?—we can agree that it would be bad to say "a user from India gave this testimonial:", or whatever—unless the place of origin is relevant, and you actually know it. I don't see much difference between these two.)
If it's posted on my website, then yes. It might not be polite or advisable, but I absolutely have the right to misgender you as well.
That being said, as an pedantic, unshorn hair, turban wearing Sikh I'm not sure I'd describe dastaarbandi as any sort of ceremony granting authorization.