Once text has been entered into the body of a message, changing the sender's Identity does not update the Signature attached to that Identity. So one has to check and select the correct Identity before entering any message text or any Signature attached to the initial Identity is not updated to match that of any new Identity. I think this happens whenever an Identity has NO Signature, whether or not it's the default or is selected after the default. Going from an Identity with Signature to one without interrupts the ability of composer to update the Signature further. I use the "--" separator and will see only the "--" for a no-Signature Identity and then no further changes are made. Reproducible: Always Steps to Reproduce: 0. Have various Identity-s, with varying or no Signatures associated. Use the "--" separator setting. 1. Open a new message. 2. Enter text in the Body 3. Change Identity Actual Results: 1. Entering body text into a message with a null-Signature Identity disables Signature changing for any Identity selected after. 2. Choosing a null-Signature Identity for a message disables Signature changing for any Identity selected after. Expected Results: Signature should track (even for null) the selection of Identity. Perhaps because I use the "Prepend separator to signature" in Configure->Composer->General?
I can confirm using KDE Applications 15.12.2, KF-based Kmail in openSUSE Tumbleweed. I hit the bug when sending attachments through dolphin. The standard identity had no signature, when I switch in composer to an identity with a signature assigned, this signature is not shown. Then I added a signature to the standard identity, and vola, the signature is updated.
Reproducible in 5.4.1 using the steps from Comment 1