The "departed" message is shown when a former elected moderator subsequently deletes their account. Since this results in a broken image being shown on the election page, staff will manually put in this placeholder image to show that there was a winner, who is no longer with the site, and to avoid the broken image icon displaying.
Stack does not plan on supporting situations of moderators deleting their accounts, however, so this is manually done every time.
Deleted candidates is not a scenario well-supported nor one we have any intention of encouraging.
I manually patched up the list of winners, which should be sufficient to indicate what happened. But we will not modify votes or alter any other data connected to the election (that is: We're not going to create fake users with fake votes winning fake positions in an old election to paper over the fact that two of the winners decided to leave; they're gone).
-Shog9 Feb 13, 2016
@Mithical one-off fix. The results are actually stored as html text in a db field. Changing it programmatically is not justified at this point. To fix it, we would have to add logic to the user deletion to parse all election results for their Id and replace it with something else. Doable but not worth it right now. – Yaakov Ellis♦ yesterday
Since this is done manually, this may lead to inconsistencies, such as the case on Software Engineering you noted in the question, where instead of the "departed" box it appears that someone opted to just show the latest version of the moderator's flair before their account was deleted.