Cannot log in using email address to WordPress.com when submitting a comment (forced to use username)

### Impacted plugin

Jetpack

### Quick summary

When attempting to submit a comment as a visitor not logged into WordPress.com on a WordPress.com site, you cannot complete the login process using an email, you must enter a username.

https://github.com/user-attachments/assets/37743a4c-b388-47ba-9a5a-9659f99713b5


### Steps to reproduce

1. Add a comment as non-logged in user
2. Enter email address used by a WordPress.com account
3. Try to login using email to the WordPress.com account

### A clear and concise description of what you expected to happen.

Account should be logged in an comment published

### What actually happened

Account was not logged in and username had to be used instead

### Impact

Some (< 50%)

### Available workarounds?

No and the platform is unusable

### If the above answer is "Yes...", outline the workaround.

_No response_

### Platform (Simple and/or Atomic)

Simple

### Logs or notes

Reported in 8834405-zd-a8c

Start by reproducing the Jetpack comment submission flow on a WordPress.com Simple site as an unauthenticated visitor, following the listed steps. Trace the WordPress.com login entry point used during comment submission; done means an account email successfully authenticates and the comment is published without requiring a username.

Written by the indexing model from the issue text.