Markdown uses punctuation to mark text for a certain format or style. In Obsidian,
- * or _ for italic
- ** or __ for bold
- ~~ for strikethrough
But why be limited to just these symbols and stylings? Some markdown editors/renderers, for example, use ++ for highlighting.
Could this be something a user sets up on their own? Could there be a plugin that lets you assign a symbol to an HTML class?
A user would designate a symbol–class pair in the plugin, and then either in the plugin or separately, they could assign CSS styling to that class.