I just downloaded and installed MarkdownPad, and I must say that I am quite impressed with how polished it is.
But, I, too would like the ability to set underscores as the default for emphasis, as where I ultimately need to paste the markdown that is generated, does not support asterisks for emphasis, only underscores.
Without the ability to over-ride the default, I would need to manually add the underscores, instead of using the button on the toolbar, which kind of defeats the whole purpose of using MarkdownPad. If I am going to have to write my own markdown, I might as well just use a basic plain text editor, like Notepad.
Additionally, there are 2 other defaults I'd like to be able to over-ride:
I am not sure what other people are using Markdown Pad for, but I am using it as a speed tool, to be able to format my text with the necessary markdown, so I can then copy and paste it where I need to use it. Once I hit the submit button, I don't get the chance to fix it (there is no edit), so it needs to be done right the first time, before it gets submitted.
If the post editor where I need to paste it had a formatting toolbar and a preview panel (like this forum), I wouldn't have gone looking for a markdown editor.
I know what you said about the markdown specifications, but that really doesn't apply to or help any of us that have to use the resulting markdown in places that don't follow the specifications to the letter. If we can't over-ride the defaults with custom rules that match our specific use cases, then we ultimately end up with unusable markdown code that will result in HTML code that will absolutely be rendered incorrectly, which makes using MarkdownPad, pointless.