Is there any notion of unique identification in the fediverse?
PabloDiscobar@kbin.social to 
Fediverse@kbin.social – 4 points – I mean between tools, no instances.
I want to share pictures (pixelfed) and videos (peertube), do have to create an account on one instance of each tool that I want to use? Is there a single point of entry somewhere?
At the moment, you have to create separate accounts for each service. It may be theoretically possible to distinguish account hosting from service provision, but at the moment, nearly all accounts are hosted by the same software that provides the service (e.g. pixelfed, peertube, kbin), and no service that I know of allows you to authenticate from a different service.
Not sure about peertube or pixelfed, but I am sending this post from Mastodon, so depending on the situation you can.
Because mastodon and kbin are both instances of the same tools (forum/microblogging)
It's not the fediverse's job to do that any more than it is HTTP's job to make sure that the person posting on Instagram and the person posting on TikTok are the same person.
Individual instances can choose whether or not to implement identity verification.
And yeah, I can "try" to impersonate you, just like I could with email. I could spin up a cheap domain and make an email address PabloDiscobar@impersonatePabloDiscobar.site .
I would like to see folks from outside of the instance more clearly marked with where they came from, though.
No. You have to make an account for each tool. The federation part comes in that I can follow a bookwyrm account on mastodon and get reading updates. But if I want to post books I'm reading, I'll need to go make an account.