@maiyannah You could perhaps construct some cookie magic that remembers who you tried to subscribe to and when the browser gets back compares it automagically... Assuming you're originally subscribing _from_ your own node.
But you can absolutely _not_ trust that a remote site's "remote subscribe by putting your URL here" will actually give you that remote profile's proper identity when you return to your own domain.
(there is however something that occasionally(?) causes you to have to put your remote address in twice _on_ the remote node... in !qvitter first and then !gnusocial... that could probably be fixed :))