I tend to write italics with underscores and bold with asterisks because it makes it even more visually obvious when just glancing at the content. I also tend to use shortcut commands when available, such as cmd
+i
to italicize the text.
Not sure what the plans are for configuration, but it would be great to be able to customize the default marks for keyboard shortcuts, e.g. cmd
+i
wraps a word in underscores.