Well, didn't make it out of town today after all, so I took a few minutes to pull down and set up a fresh copy of SVN 3031 and patched it.
Obviously, I'll want to do more testing over a longer period, but at first glance it looks like a really good start. In fact, the actual top posting part looks to be pretty solid. Much better than any of the hacks people did to v.0.2.
The "insert signature" part works, but looking at it as if I was one of my non-technical users, I see a couple of glitches.
One is that the "Insert" button looks available even when it's not. For example, if the signature is set to auto-insert (set to always, for example), the "insert" button correctly does nothing. But it is still visible, and is not grayed out. Ideally, the button would only be visible if the option was available, or at least grayed out.
But the larger issue is that if the users' pref is set to top post, clicking the "Insert" button inserts the sig at the very beginning of the message. This would be fine if the user clicked the button before beginning to compose. But if the user types in their message, and then clicks the button, the sig is inserted at the top, above the message the user just typed.
I strongly suspect that your average email user is going to expect that the "insert" button would insert the sig at the cursor position within the text editor box. And in hind sight, that probably isn't possible, as the insert routine needs to grab the contents of the text editor, add the sig and then reload it. (Or so it would seem to me.) If that truly is the case, I fear the "insert" button will cause confusion and frustration for normal users, and might be best abandoned.