As an experiment, I sent myself a new message to the account exhibiting the behavior. When I click on the specific email that is showing this behavior, the message I just sent from another account got appended to the body of the culprit email but only if I clicked and viewed the newly arrived message. I'm willing to send this offending email privately to someone as proof that I am not going nuts. Full disclosure, I installed 94.0b5 this morning.
Bug 1738105 Comment 1 Edit History
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As an experiment, I sent myself a new message to the account exhibiting the behavior. When I click on the specific email that is showing this behavior, the message I just sent from another account got appended to the body of the culprit email. I'm willing to send this offending email privately to someone as proof that I am not going nuts. Full disclosure, I installed 94.0b5 this morning.