Markdown helpers for the comment block

I submit a lot of posts from mobile, and I find some of the markdown tedious to enter on a mobile keyboard. I know JavaScript is supposed to be a last resort, but I'd really like to have some assistance in the post authoring and comments fields.

I assume this could be a user script. Looking at the wiki, it looks like none of the current ones do this.

Thoughts on this? Things people are already using? Ideas for existing tools to build on? Would it be better as a user script or as a feature of the main site, perhaps with an option to disable it? I'm medium at JavaScript but would happily take a crack at it.

Here is my inital feature list:

• link button - select text, press the link button, get a prompt for the URL, replace the selected text with the markdown formatted text and URL.
• quote block- select multiple paragraphs and click the button to block quote them all
• bold, italic, strike though buttons - apply the markdown to selected text
• spoiler - insert a details block at the cursor. If text is selected wrap it in a details block and prompt for the summary.

if I were to develop it, what else would people like to see on this list?