Read:
https://en.wikipedia.org/wiki/Ident_protocol
What this "~donaldtrump@255.255.255.255.global.comcast.net" is, is an ident string, where in this example, 'donaldtrump' is the actual ident value.
ident is essentially the identifier of who started the TCP connection from the client to the server.
You're not running identd, hence the tilde in front of the string, and you shouldn't be. This ident is being generated by the client application (as opposed to identd). What the client application is pulling from your environment variables to provide to the service will vary. I have no idea what the context of your question is, so I'm going to answer in terms of IRC, since IRC is the most common occurrence of ident.
IRC clients will simulate identd and respond to ident requests from the server. *Usually*, it'll just grab the value of the username environment variable, and ship that over. Some clients will have this hard coded, so your ident string will actually end up being 'younick!somedefaultstring@yourdomain'. In any case, you should be able to locate a setting in your IRC client to set this value to whatever you want.
Going back to your statement that: "even if u do /nick hillaryclinton that doesnt effect how ~donaldtrump@177.0.0.1.comcast.net is displayed"
That is actually normal behavior. Changing your nick on IRC shouldn't change your ident value. Going back to the ident protocol, and what was stated earlier, ident is who started the TCP connection. Thus, this will typically be the username of the person on the client computer. A 'nick' on IRC is just the person's identifier on IRC. Thus, an ident and an IRC nick are independent identifiers. It's not uncommon for users to have the same ident and IRC nick. Your username on your local machine might be donald, while your IRC nick is donaldtrump, and thus, your full ident string on IRC will be donald!
donaldtrump@mydomain.net.
