Because let’s say you’re Tom Hanks. And you get TomHanks@Lemmy.World
Well, what’s stopping someone else from adopting TomHanks@Lemm.ee?
And some platforms minimize the text size of platform, or hide it entirely. So you just might see TomHanks, and think it’s him. But it’s actually a 7 year old Chinese boy with a broken leg in Arizona.
Because anyone can grab the same name, on a different platform.
Even without federation and such it’s an issue. Old twitter actually did a really good job of this, but other social networks have had problems in the past,
https://www.dailydot.com/debug/katie-hopkins-impersonated-parler/
https://www.politico.com/news/2020/07/02/republicans-parler-trolls-347737
We don’t have to guess if trolls will try to impersonate celebs and be successful at it, because it’s already happened elsewhere.
That said, there are two nice things about the fediverse. First, verification is explicitly not offered, so folks have to do the digging themselves to see if an account is official or not. (Which is as easy as checking a person’s web site). Or perhaps confusing a regular person’s account with a celeb of the same name.
Second, you can host your own instance. Celebs might not bother, but official gov’t agencies set up their own domains and websites - and in particular under domains like .gov which aren’t open to regular folks. So seeing if a gov’t agency is really authentic is potentially as simple as checking the domain that the instance is using.