@reply UI should allow arbitrary content types

[cdent]

Copied from tiddlyspace/#935, original by @FND , see the comments there

pretty much like edit

I don't like TiddlyWiki markup, so I use Markdown instead - using @reply currently forces me to drop into @edit post-creation to modify the content type.

[pads]

Ignore the reference above, it should be 9 not 6