Two-factor authentication has idiotic limitation.

When setting up an email account, you are (quite sensibly) asked to set up 2-factor authentication.  You can have either a phone number or an email account.  Fine.
Except, not fine.  I have one phone number and five email addresses in my Xfinity account.  For whatever reason, the system will not let you use one phone number on more than one email address.  So that means I have to log in to a non-comcast email address to be able to read my comcast email.

So...why would I do that?  Why would I use comcast email at all, since I already have to be logged in to gmail to get access.  This issue gets doubly obnoxious when trying to read mail on my phone.

This is value-subtracted thinking that drives customers away.  Fix it!