Selected mailboxes are now bold (Apple Mail) - Did I do this?

[EnzoFX]

So I noticed this today, and I have no idea how the text became bold. It is on a selected item from the left pane, as visible here:

Not a problem, but I am curious =P.

 

[tersono]

Uhm... that would be because the mailbox contains unread items.... 🙄

 

[EnzoFX]

Nope, no unread mails, happens with all items on the left panel, unread or not.