TL;DR - Please change the behavior so that once a user signs up, the questions posted from a guest account with the same e-mail will be linked to the signed up user.
After posting 2 questions as guest, I signed up. The experience I had after signing up was is extremely frustrating.
I asked a question. As a result, I got a mail suggesting that I will sign up. I signed up. The questions I asked using the same e-mail address as guest were not linked with my account, and are still considered posted by the guest user. Because the signed up account is a new account, I have no reputation, so I can't comment on other users' questions. This means that once I signed up, I was no longer able to participate in the discussion about the questions I asked.
In order to give this feedback, I need 5 reputation, which I initially didn't have,. This is frustrating mostly because the "feedback" link in the mail I got directed me here. While the mail gives the impression I can provide feedback, in practice I couldn't.
In addition, until I cleared the browser cookies, the account was in flux. I couldn't properly operate as the guest, because the e-mail address belonged to another user. I found no way to switch to the signed up account (I tried to complete signing in, several times, ending up exactly where I started), so I couldn't operate as the signed up account as well.
Fortunately enough, I got some comments on my question and ended up editing it twice. Due to this, I now have enough reputation to post here about the user experience I had.
The overall experience is that once you sign up, you have less capabilities than a guest. A user should not lose capabilities when signing up.
Please change the behavior so that once a user signs up, the questions posted from a guest account with the same e-mail will be linked to the signed up user.
(my intention is not to aimlessly complain, but to give actionable feedback on the user experience; I apologize if this ended up sounding like a long rant)