iOS 7 brought a lot of changes regarding keyboard handling.

This will be fixed in the next update: the additional keys will always stay on the screen, but you can disable it in settings and the UI will be completely usable even with the additional keys displayed.

Ah, sorry, I thought you were talking about the iOS version. The Mac version doesn't have Markdown preview and export support at the moment.

You can use the excellent Marked app for this purpose: http://marked2app.com

You can already do that: when you have a Markdown file open, you can select the action button and "Copy generated HTML". This will copy the HTML code to the clipboard.

I plan to release it together with the iOS 7 update. I don't have a specific date for you at the moment.

I plan to add support for the new TextExpander SDK in the next update.

Actually, this board is very active. Have a look at the "Latest Updates" section at http://feedback.textasticapp.com or at http://feedback.textasticapp.com/list/1158-textas...

The code completions files can be found at https://github.com/blach/Textastic-Customization

You can modify the "br" behavior by changing the "defaultAppend" string in line 165 (https://github.com/blach/Textastic-Customization/b...

Syntax definitions can be found by searching for "<languagename> tmbundle". Textastic supports textmate 1 syntax definitions. For example, the HTML syntax definition can be found at https://github.com/textmate/html.tmbundle/tree/textmate-1.x

I think that's outside the scope of Textastic. It would propably be more appropriate for a separate app.