I found this Post when searching through the web because I am facing the exact same problem.
However, appending a white space to the end of the node was not an option, and I found an alternative way that seems to fix the issue.
After setting my node font Bold, all I need to do is reset the node text with the same value.
Here is the Code Sample:
Font boldFont = new Font(treeview.Font, FontStyle.Bold);
node.NodeFont = boldFont;
node.Text = node.Text;
It seems that the node is redrawn after changing the text, which is exactly what I wanted in the first place.