When creating a reply to an email, kmail consults the list of addressees of that email to match an identity to use for the new reply - if it fails to find a match, it chooses the identity based on the setting of the folder the email is in. It seems that in this latter situation, it doesn't matter if the *parent* folder has a non-global-default identity specified.
I could be wrong, but I feel like it used to be the case that if any parent folder has a non-default identity specified, this would cascade to child folders. Certainly this would make more sense to me as the default behaviour, at least in my use-case - I have multiple accounts with different identities specified at the top level (account) folder, but unless I were to set each folder individually to use the applicable non-global-default identity, this is ignored.
I would like to see identity settings cascade into subfolders, but on further reflection I think "Use default identity" would make more sense split-up into three options: 1. Use global default identity (i.e., the current behaviour), 2. Use parent folder identity (IMO the better behaviour to have as default), 3. Use another identity (user choice goes here).
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