This happened to me more than a few times while trying to file an email to a folder, and during the process, I accidentally hit some random keys on the keyboards, and Yahoo! Mail deleted the email which I was filing and some subsequent emails. I finally able to reproduce it more consistently by typing a number of characters and hit the backspace key once or a number of times and repeated that sequence if needed. This is awful that emails were deleted during the filing when you hit the wrong keys. As I'm typing this, I realized the problem must have occurred when I was filing an email, and I entered the incorrect folder name, and backspacing it to correct resulted in emails being deleted.

When trying to move selected email to a folder by typing its name in the folder selector, if I hit the backspace button to correct a letter I typed it deletes the email.

Hitting the backspace while typing a folder name should not delete the email.

When typing, or when trying to move an email to another folder, if the Backspace is used at any given time, it will delete the email. If the backspace is held to delete a whole word/sentence, it will delete everything in the inbox... The appearance will also randomly switch to darkmode. We have not pinpointed what causes it, but it has happened at least twice a week for a little while now.

Please, disable short-cuts by default. For example in case if focus is on email window by mistake and I press backspace it has catastrophic consequences. If somebody needs such functionality he/she can enable it in settings ...
Thanks