Following the advice here How do I delete a local branch on Github Desktop? I went ahead and deleted some dead branches on the github website. The problem is that others can still see them. I was told that this is because the branches are still on my local repository, but when I look at Github Desktop, it asks me if I want to publish these dead branches, which makes me think they should not currently be visible.
What could be going on here?
It's most of a year since the original question, but I just started using github desktop and I see the problem too. Did you ever find an answer? Maybe this is all by design: just because you delete the remote branch doesn't necessarily mean you wanted to delete the local branch.
Interesting: if I try to delete the branch from the gear menu in github desktop within a few minutes after having deleted it on the website, github desktop brings up a dialog saying the branch exists on both local and remote and asks if I'd like to delete both. Canceling from that and then trying the same delete branch item from the gear menu a few minutes later, it does not bring up that dialog and just silently deletes the local branch. I had hit 'Sync' a few times in that intervening time, so maybe that's what did it.
