Hi @blastframe,
so this is a bug that happens independently of Python. It also not connected to your example using a dangling dialog, but to the fact that it is using a dialog. When you implement some form of NodeData plugin and a FONT resource element in it, this bug won't happen.
I have opened a bug report for this. For now you would have to either use my little workaround or move outside of a GeDialog environment an implement the whole plugin as some form of NodeData plugin. If a dialog is of high priority for you, you could also display an instance of that node in a DescriptionCustomGui inside your dialog. Which should work and somewhat be a mix of both options.
Cheers,
Ferdinand